KSH(1)                           User commands                          KSH(1)



NAME
       ksh - Public domain Korn shell

SYNOPSIS
       ksh [+-abCefhikmnprsuvxX] [+-o option] [ [ -c command-string [command-
       name] | -s | file ] [argument ...] ]

DESCRIPTION
       ksh is a command interpreter that is intended for both interactive  and
       shell  script  use.   Its  command  language is a superset of the sh(1)
       shell language.

   Shell Startup
       The following options can be specified only on the command line:

       -c command-string
              the shell executes the command(s) contained in command-string

       -i     interactive mode -- see below

       -l     login shell -- see below interactive mode -- see below

       -s     the shell reads commands from  standard  input;  all  non-option
              arguments are positional parameters

       -r     restricted mode -- see below

       In  addition  to  the  above, the options described in the set built-in
       command can also be used on the command line.

       If neither the -c nor the -s options  are  specified,  the  first  non-
       option  argument  specifies the name of a file the shell reads commands
       from; if there are no non-option arguments, the  shell  reads  commands
       from  standard input.  The name of the shell (i.e., the contents of the
       $0) parameter is determined as follows: if the -c option  is  used  and
       there is a non-option argument, it is used as the name; if commands are
       being read from a file, the file is used as  the  name;  otherwise  the
       name the shell was called with (i.e., argv[0]) is used.

       A  shell  is  interactive  if the -i option is used or if both standard
       input and standard error are attached to a tty.  An  interactive  shell
       has  job control enabled (if available), ignores the INT, QUIT and TERM
       signals, and prints prompts before  reading  input  (see  PS1  and  PS2
       parameters).   For non-interactive shells, the trackall option is on by
       default (see set command below).

       A shell is restricted if the -r option is used or if either  the  base-
       name of the name the shell is invoked with or the SHELL parameter match
       the pattern *r*sh (e.g.,  rsh,  rksh,  rpdksh,  etc.).   The  following
       restrictions come into effect after the shell processes any profile and
       $ENV files:
         o    the cd command is disabled
         o    the SHELL, ENV and PATH parameters can't be changed
         o    command names can't be specified with absolute or relative paths
         o    the -p option of the command built-in can't be used
         o    redirections  that  create files can't be used (i.e., >, >|, >>,
              <>)

       A shell is privileged if the -p option is used or if the  real  user-id
       or  group-id  does  not  match  the  effective user-id or group-id (see
       getuid(2), getgid(2)).  A privileged shell does not process $HOME/.pro-
       file nor the ENV parameter (see below), instead the file /etc/suid_pro-
       file is processed.  Clearing the privileged option causes the shell  to
       set its effective user-id (group-id) to its real user-id (group-id).

       If  the  basename  of the name the shell is called with (i.e., argv[0])
       starts with - or if the -l option is used, the shell is assumed to be a
       login  shell and the shell reads and executes the contents of /etc/pro-
       file, $HOME/.profile and $ENV if they exist and are readable.

       If the ENV parameter is set when the shell starts (or, in the  case  of
       login shells, after any profiles are processed), its value is subjected
       to parameter,  command,  arithmetic  and  tilde  substitution  and  the
       resulting  file (if any) is read and executed.  If the ENV parameter is
       not set (and not null) the file $HOME/.kshrc  is  included  (after  the
       above mentioned substitutions have been performed).

       The  exit  status  of the shell is 127 if the command file specified on
       the command line could not be opened, or non-zero  if  a  fatal  syntax
       error  occurred  during  the  execution of a script.  In the absence of
       fatal errors, the exit status is that of the last command executed,  or
       zero, if no command is executed.

   Command Syntax
       The  shell  begins parsing its input by breaking it into words.  Words,
       which are sequences of characters, are  delimited  by  unquoted  white-
       space  characters (space, tab and newline) or meta-characters (<, >, |,
       ;, &, ( and )).  Aside from  delimiting  words,  spaces  and  tabs  are
       ignored,  while newlines usually delimit commands.  The meta-characters
       are used in building the following tokens: <, <&, <<, >, >&,  >>,  etc.
       are  used to specify redirections (see Input/Output Redirection below);
       | is used to create pipelines; |& is used to create  co-processes  (see
       Co-Processes  below); ; is used to separate commands; & is used to cre-
       ate asynchronous pipelines; && and || are used to  specify  conditional
       execution;  ;;  is used in case statements; (( .. )) are used in arith-
       metic expressions; and lastly, ( .. ) are used to create subshells.

       White-space and meta-characters can be quoted individually using  back-
       slash  (\),  or  in groups using double (") or single (') quotes.  Note
       that the following characters are also treated specially by  the  shell
       and  must be quoted if they are to represent themselves: \, ", ', #, $,
       `, ~, {, }, *, ? and [.  The first three of these are  the  above  men-
       tioned quoting characters (see Quoting below); #, if used at the begin-
       ning of a word, introduces a comment -- everything after the  #  up  to
       the  nearest newline is ignored; $ is used to introduce parameter, com-
       mand and arithmetic substitutions (see Substitution  below);  `  intro-
       duces  an  old-style  command  substitution (see Substitution below); ~
       begins a directory expansion (see  Tilde  Expansion  below);  {  and  }
       delimit  csh(1)  style  alternations  (see Brace Expansion below); and,
       finally, *, ? and [ are used in file name  generation  (see  File  Name
       Patterns below).

       As  words  and  tokens  are parsed, the shell builds commands, of which
       there are two basic types: simple-commands, typically programs that are
       executed,  and compound-commands, such as for and if statements, group-
       ing constructs and function definitions.

       A simple-command consists of some combination of parameter  assignments
       (see  Parameters  below),  input/output  redirections (see Input/Output
       Redirections below), and command words; the only  restriction  is  that
       parameter  assignments  come  before  any  command  words.  The command
       words, if any, define the command that is to be executed and its  argu-
       ments.   The  command may be a shell built-in command, a function or an
       external command, i.e., a separate  executable  file  that  is  located
       using  the PATH parameter (see Command Execution below).  Note that all
       command constructs have an exit status: for external commands, this  is
       related  to the status returned by wait(2) (if the command could not be
       found, the exit status is 127, if it could not be  executed,  the  exit
       status  is  126); the exit status of other command constructs (built-in
       commands, functions, compound-commands, pipelines, lists, etc.) are all
       well  defined  and are described where the construct is described.  The
       exit status of a command consisting only of  parameter  assignments  is
       that  of  the  last command substitution performed during the parameter
       assignment or zero if there were no command substitutions.

       Commands can be chained together using the | token to  form  pipelines,
       in which the standard output of each command but the last is piped (see
       pipe(2)) to the standard input of the following command.  The exit sta-
       tus  of a pipeline is that of its last command.  A pipeline may be pre-
       fixed by the ! reserved word which causes the exit status of the  pipe-
       line  to  be  logically  complemented: if the original status was 0 the
       complemented status will be 1, and if the original status  was  not  0,
       then the complemented status will be 0.

       Lists  of commands can be created by separating pipelines by any of the
       following tokens: &&, ||, &, |& and ;.  The first two  are  for  condi-
       tional execution: cmd1 && cmd2 executes cmd2 only if the exit status of
       cmd1 is zero; || is the opposite -- cmd2 is executed only if  the  exit
       status  of  cmd1 is non-zero.  && and || have equal precedence which is
       higher than that of &, |& and ;, which also have equal precedence.  The
       &  token  causes  the  preceding command to be executed asynchronously,
       that is, the shell starts the command, but does not wait for it to com-
       plete (the shell does keep track of the status of asynchronous commands
       -- see Job Control below).  When an  asynchronous  command  is  started
       when  job  control  is disabled (i.e., in most scripts), the command is
       started with signals INT and QUIT ignored  and  with  input  redirected
       from  /dev/null  (however,  redirections  specified in the asynchronous
       command have precedence).  The |& operator starts a co-process which is
       special  kind  of  asynchronous process (see Co-Processes below).  Note
       that a command must follow the && and ||  operators,  while  a  command
       need  not follow &, |& and ;.  The exit status of a list is that of the
       last command executed, with the exception of  asynchronous  lists,  for
       which the exit status is 0.

       Compound  commands  are  created  using the following reserved words --
       these words are only recognized if they are unquoted and  if  they  are
       used  as  the  first word of a command (i.e., they can't be preceded by
       parameter assignments or redirections):

                         case   else   function   then    !
                         do     esac   if         time    [[
                         done   fi     in         until   {
                         elif   for    select     while   }
       Note: Some shells (but not this one) execute control structure commands
       in  a  subshell  when  one  or more of their file descriptors are redi-
       rected, so any environment changes inside them may fail.  To be  porta-
       ble,  the  exec  statement  should  be  used  instead  to redirect file
       descriptors before the control structure.

       In the following compound command descriptions, command lists  (denoted
       as  list)  that  are  followed  by reserved words must end with a semi-
       colon, a newline or a (syntactically correct) reserved word.  For exam-
       ple,
              { echo foo; echo bar; }
              { echo foo; echo bar<newline>}
              { { echo foo; echo bar; } }
       are all valid, but
              { echo foo; echo bar }
       is not.

       ( list )
              Execute  list  in  a subshell.  There is no implicit way to pass
              environment changes from a subshell back to its parent.

       { list }
              Compound construct; list is executed, but  not  in  a  subshell.
              Note that { and } are reserved words, not meta-characters.

       case word in [ [(] pattern [| pattern] ... ) list ;; ] ... esac
              The  case statement attempts to match word against the specified
              patterns;  the  list  associated  with  the  first  successfully
              matched  pattern  is executed.  Patterns used in case statements
              are the same as those used for file name  patterns  except  that
              the  restrictions  regarding . and / are dropped.  Note that any
              unquoted space before and after a pattern is stripped; any space
              with  a  pattern must be quoted.  Both the word and the patterns
              are subject to parameter, command, and  arithmetic  substitution
              as well as tilde substitution.  For historical reasons, open and
              close braces may be used instead of in and esac (e.g., case $foo
              {  *) echo bar; }).  The exit status of a case statement is that
              of the executed list; if no list is executed, the exit status is
              zero.

       for name [ in word ... term ] do list done
              where  term  is  either  a newline or a ;.  For each word in the
              specified word list, the parameter name is set to the  word  and
              list is executed.  If in is not used to specify a word list, the
              positional parameters ("$1", "$2", etc.) are used instead.   For
              historical reasons, open and close braces may be used instead of
              do and done (e.g., for i; { echo $i; }).  The exit status  of  a
              for  statement is the last exit status of list; if list is never
              executed, the exit status is zero.

       if list then list [elif list then list] ... [else list] fi
              If the exit status of the first list is zero, the second list is
              executed; otherwise the list following the elif, if any, is exe-
              cuted with similar consequences.  If all the lists following the
              if  and  elifs  fail (i.e., exit with non-zero status), the list
              following the else is executed.  The exit status of an if state-
              ment  is  that  of  non-conditional list that is executed; if no
              non-conditional list is executed, the exit status is zero.

       select name [ in word ... term ] do list done
              where term is either a newline or a  ;.   The  select  statement
              provides  an automatic method of presenting the user with a menu
              and selecting from it.  An  enumerated  list  of  the  specified
              words  is  printed on standard error, followed by a prompt (PS3,
              normally `#? ').  A number corresponding to one of  the  enumer-
              ated  words is then read from standard input, name is set to the
              selected word (or is unset if the selection is not valid), REPLY
              is  set  to  what was read (leading/trailing space is stripped),
              and list is executed.  If a blank line (i.e., zero or  more  IFS
              characters) is entered, the menu is re-printed without executing
              list.  When list completes, the enumerated list  is  printed  if
              REPLY is null, the prompt is printed and so on.  This process is
              continues until an end-of-file is read, an interrupt is received
              or  a  break  statement is executed inside the loop.  If in word
              ... is omitted, the positional parameters are used (i.e.,  "$1",
              "$2",  etc.).  For historical reasons, open and close braces may
              be used instead of do and done (e.g., select i; { echo  $i;  }).
              The  exit status of a select statement is zero if a break state-
              ment is used to exit the loop, non-zero otherwise.

       until list do list done
              This works like while, except that the  body  is  executed  only
              while the exit status of the first list is non-zero.

       while list do list done
              A  while is a prechecked loop.  Its body is executed as often as
              the exit status of the first list is zero.  The exit status of a
              while  statement is the last exit status of the list in the body
              of the loop; if the body is not executed,  the  exit  status  is
              zero.

       function name { list }
              Defines  the  function  name.   See  Functions below.  Note that
              redirections specified after a function definition are performed
              whenever the function is executed, not when the function defini-
              tion is executed.

       name () command
              Mostly the same as function.  See Functions below.

       time [ -p ] [ pipeline ]
              The time reserved word is described  in  the  Command  Execution
              section.

       (( expression ))
              The arithmetic expression expression is evaluated; equivalent to
              let "expression".  See Arithmetic Expressions and the  let  com-
              mand below.

       [[ expression ]]
              Similar to the test and [ ... ] commands (described later), with
              the following exceptions:
                o    Field splitting and file name  generation  are  not  per-
                     formed on arguments.
                o    The  -a  (and) and -o (or) operators are replaced with &&
                     and ||, respectively.
                o    Operators (e.g., -f, =, !, etc.) must be unquoted.
                o    The second operand of != and = expressions  are  patterns
                     (e.g., the comparison in
                                        [[ foobar = f*r ]]
                     succeeds).
                o    There  are two additional binary operators: < and > which
                     return true if their first string operand is  less  than,
                     or  greater  than,  their  second string operand, respec-
                     tively.
                o    The single argument form of  test,  which  tests  if  the
                     argument  has  non-zero  length,  is not valid - explicit
                     operators must always be used, e.g., instead of
                                              [ str ]
                     use
                                           [[ -n str ]]
                o    Parameter, command and arithmetic substitutions are  per-
                     formed  as  expressions are evaluated and lazy expression
                     evaluation is used for the &&  and  ||  operators.   This
                     means that in the statement
                                  [[ -r foo && $(< foo) = b*r ]]
                     the  $(<  foo)  is  evaluated if and only if the file foo
                     exists and is readable.

   Quoting
       Quoting is used to prevent the shell from treating characters or  words
       specially.   There  are  three  methods of quoting: First, \ quotes the
       following character, unless it is at the end of a line, in  which  case
       both  the  \  and the newline are stripped.  Second, a single quote (')
       quotes everything up to the next single quote (this  may  span  lines).
       Third,  a double quote (") quotes all characters, except $, ` and \, up
       to the next unquoted double quote.  $ and ` inside double  quotes  have
       their  usual  meaning (i.e., parameter, command or arithmetic substitu-
       tion) except no field splitting is carried out on the results  of  dou-
       ble-quoted substitutions.  If a \ inside a double-quoted string is fol-
       lowed by \, $, ` or ", it is replaced by the second character; if it is
       followed  by a newline, both the \ and the newline are stripped; other-
       wise, both the \ and the character following are unchanged.

       Note: An earlier  version  of  ksh(1)  changed  the  interpretation  of
       sequences  of  the  form "...`...\"...`.."  according to whether or not
       POSIX mode was in effect.  In the current implementation, the backslash
       in  \"  is seen and removed by the outer "...", so the backslash is not
       seen by the inner `...`.

   Aliases
       There are two types of aliases:  normal  command  aliases  and  tracked
       aliases.   Command aliases are normally used as a short hand for a long
       or often used command.  The shell expands command aliases  (i.e.,  sub-
       stitutes  the alias name for its value) when it reads the first word of
       a command.  An  expanded  alias  is  re-processed  to  check  for  more
       aliases.  If a command alias ends in a space or tab, the following word
       is also checked for alias expansion.  The alias expansion process stops
       when  a word that is not an alias is found, when a quoted word is found
       or when an alias word that is currently being expanded is found.

       The following command aliases are defined automatically by the shell:
              autoload='typeset -fu'
              functions='typeset -f'
              hash='alias -t'
              history='fc -l'
              integer='typeset -i'
              local='typeset'
              login='exec login'
              nohup='nohup '
              r='fc -e -'
              stop='kill -STOP'
              suspend='kill -STOP $$'
              type='whence -v'

       Tracked aliases allow the shell to remember where it found a particular
       command.   The  first  time  the shell does a path search for a command
       that is marked as a tracked alias, it saves the full path of  the  com-
       mand.   The  next  time  the  command is executed, the shell checks the
       saved path to see that it is still valid, and if so,  avoids  repeating
       the path search.  Tracked aliases can be listed and created using alias
       -t.  Note that changing the PATH parameter clears the saved  paths  for
       all  tracked  aliases.   If  the  trackall  option is set (i.e., set -o
       trackall or set -h), the shell tracks all commands.  This option is set
       automatically for non-interactive shells.  For interactive shells, only
       the following commands are automatically tracked: cat, cc,  chmod,  cp,
       date, ed, emacs, grep, ls, mail, make, mv, pr, rm, sed, sh, vi and who.

   Substitution
       The first step the shell takes in executing a simple-command is to per-
       form  substitutions on the words of the command.  There are three kinds
       of substitution: parameter, command and arithmetic.  Parameter  substi-
       tutions,  which  are  described in detail in the next section, take the
       form $name or ${...}; command substitutions take the form $(command) or
       `command`;  and arithmetic substitutions take the form $((expression)).

       If a substitution appears outside of double quotes, the results of  the
       substitution are generally subject to word or field splitting according
       to the current value of the IFS parameter.  The IFS parameter specifies
       a  list  of characters which are used to break a string up into several
       words; any characters from the set space, tab and newline  that  appear
       in  the IFS characters are called IFS white space.  Sequences of one or
       more IFS white space characters, in combination with zero or  one  non-
       IFS white space characters delimit a field.  As a special case, leading
       and trailing IFS white space is stripped (i.e., no leading or  trailing
       empty  field is created by it); leading or trailing non-IFS white space
       does create an empty field.  Example: if IFS is set to `<space>:',  the
       sequence  of  characters  `<space>A<space>:<space><space>B::D' contains
       four fields: `A', `B', `' and `D'.  Note that if the IFS  parameter  is
       set to the null string, no field splitting is done; if the parameter is
       unset, the default value of space, tab and newline is used.

       The results of substitution are, unless otherwise specified, also  sub-
       ject  to brace expansion and file name expansion (see the relevant sec-
       tions below).

       A command substitution is replaced by the output generated by the spec-
       ified  command,  which  is run in a subshell.  For $(command) substitu-
       tions, normal quoting rules are used when command is  parsed,  however,
       for the `command` form, a \ followed by any of $, ` or \ is stripped (a
       \ followed by any other character is unchanged).  As a special case  in
       command  substitutions,  a command of the form < file is interpreted to
       mean substitute the contents of file ($(< foo) has the same  effect  as
       $(cat  foo),  but it is carried out more efficiently because no process
       is started).
       NOTE: $(command) expressions are currently parsed by finding the match-
       ing  parenthesis,  regardless of quoting.  This will hopefully be fixed
       soon.

       Arithmetic substitutions are replaced by the  value  of  the  specified
       expression.   For  example, the command echo $((2+3*4)) prints 14.  See
       Arithmetic Expressions for a description of an expression.

   Parameters
       Parameters are shell variables; they can be assigned values  and  their
       values  can  be  accessed  using a parameter substitution.  A parameter
       name is either one of the special single punctuation or digit character
       parameters  described  below, or a letter followed by zero or more let-
       ters or digits (`_' counts as a letter).  The later form can be treated
       as arrays by appending an array index of the form: [expr] where expr is
       an arithmetic expression.  Array indices are currently limited  to  the
       range 0 through 1023, inclusive.  Parameter substitutions take the form
       $name, ${name} or ${name[expr]}, where name is a  parameter  name.   If
       substitution  is  performed  on a parameter (or an array parameter ele-
       ment) that is not set, a null string is substituted unless the  nounset
       option  (set  -o  nounset  or  set  -u)  is set, in which case an error
       occurs.

       Parameters can be assigned values in a  number  of  ways.   First,  the
       shell  implicitly  sets  some parameters like #, PWD, etc.; this is the
       only way the special single  character  parameters  are  set.   Second,
       parameters  are  imported  from  the  shell's  environment  at startup.
       Third, parameters can be assigned values on the command line, for exam-
       ple,  `FOO=bar'  sets  the  parameter  FOO  to  bar; multiple parameter
       assignments can be given on a single command line and they can be  fol-
       lowed  by a simple-command, in which case the assignments are in effect
       only for the  duration  of  the  command  (such  assignments  are  also
       exported,  see  below  for  implications  of this).  Note that both the
       parameter name and the = must be unquoted for the shell to recognize  a
       parameter  assignment.   The  fourth way of setting a parameter is with
       the export, readonly and typeset commands; see  their  descriptions  in
       the Command Execution section.  Fifth, for and select loops set parame-
       ters as well as the getopts, read and set -A commands.  Lastly, parame-
       ters  can  be  assigned values using assignment operators inside arith-
       metic expressions (see  Arithmetic  Expressions  below)  or  using  the
       ${name=value} form of parameter substitution (see below).

       Parameters  with  the export attribute (set using the export or typeset
       -x commands, or by parameter assignments followed by  simple  commands)
       are  put  in  the  environment  (see environ(7)) of commands run by the
       shell as name=value pairs.  The order in which parameters appear in the
       environment  of a command is unspecified.  When the shell starts up, it
       extracts parameters and their values from its environment and automati-
       cally sets the export attribute for those parameters.

       Modifiers can be applied to the ${name} form of parameter substitution:

       ${name:-word}
              if name is set and not null, it is substituted,  otherwise  word
              is substituted.

       ${name:+word}
              if  name  is  set  and  not null, word is substituted, otherwise
              nothing is substituted.

       ${name:=word}
              if name is set and not null, it is substituted, otherwise it  is
              assigned word and the resulting value of name is substituted.

       ${name:?word}
              if  name  is set and not null, it is substituted, otherwise word
              is printed on standard error (preceded by name:)  and  an  error
              occurs (normally causing termination of a shell script, function
              or .-script).  If word is omitted the string `parameter null  or
              not set' is used instead.

       In  the above modifiers, the : can be omitted, in which case the condi-
       tions only depend on name being set (as opposed to set and  not  null).
       If  word  is needed, parameter, command, arithmetic and tilde substitu-
       tion are performed on it; if word is not needed, it is not evaluated.

       The following forms of parameter substitution can also be used:

       ${#name}
              The number of positional parameters if name is *, @  or  is  not
              specified,  or the length of the string value of parameter name.

       ${#name[*]}, ${#name[@]}
              The number of elements in the array name.

       ${name#pattern}, ${name##pattern}
              If pattern matches the beginning of the value of parameter name,
              the  matched text is deleted from the result of substitution.  A
              single # results in the shortest match, two #'s results  in  the
              longest match.

       ${name%pattern}, ${name%%pattern}
              Like  ${..#..}  substitution, but it deletes from the end of the
              value.

       The following special parameters are implicitly set by  the  shell  and
       cannot be set directly using assignments:

       !      Process  id of the last background process started.  If no back-
              ground processes have been started, the parameter is not set.

       #      The number of positional parameters (i.e., $1, $2, etc.).

       $      The process ID of the shell, or the PID of the original shell if
              it is a subshell.

       -      The  concatenation of the current single letter options (see set
              command below for list of options).

       ?      The exit status of the last non-asynchronous  command  executed.
              If  the  last  command  was killed by a signal, $? is set to 128
              plus the signal number.

       0      The name the shell was invoked with (i.e., argv[0]), or the com-
              mand-name  if it was invoked with the -c option and the command-
              name was supplied, or the file argument, if it was supplied.  If
              the posix option is not set, $0 is the name of the current func-
              tion or script.

       1 ... 9
              The first nine positional parameters that were supplied  to  the
              shell,  function or .-script.  Further positional parameters may
              be accessed using ${number}.

       *      All positional parameters (except  parameter  0),  i.e.,  $1  $2
              $3....   If  used outside of double quotes, parameters are sepa-
              rate words (which are subjected  to  word  splitting);  if  used
              within  double  quotes,  parameters  are  separated by the first
              character of the IFS parameter (or the empty string  if  IFS  is
              null).

       @      Same  as  $*,  unless  it is used inside double quotes, in which
              case a separate word is generated for each positional  parameter
              -  if  there  are no positional parameters, no word is generated
              ("$@" can be used to access arguments, verbatim, without  losing
              null arguments or splitting arguments with spaces).

       The following parameters are set and/or used by the shell:

       _ (underscore)
              When  an external command is executed by the shell, this parame-
              ter is set in the environment of the new process to the path  of
              the  executed  command.   In  interactive use, this parameter is
              also set in the parent shell to the last word  of  the  previous
              command.   When  MAILPATH messages are evaluated, this parameter
              contains the name of the file that changed (see MAILPATH parame-
              ter below).

       CDPATH Search  path for the cd built-in command.  Works the same way as
              PATH for those directories not beginning with / in cd  commands.
              Note  that  if CDPATH is set and does not contain . nor an empty
              path, the current directory is not searched.

       COLUMNS
              Set to the number of columns on the terminal  or  window.   Cur-
              rently  set  to  the  cols  value as reported by stty(1) if that
              value is non-zero.  This parameter is used  by  the  interactive
              line  editing  modes, and by select, set -o and kill -l commands
              to format information in columns.

       EDITOR If the VISUAL parameter is not set, this parameter controls  the
              command  line  editing  mode for interactive shells.  See VISUAL
              parameter below for how this works.

       ENV    If this parameter is found to be set after any profile files are
              executed,  the  expanded value is used as a shell start-up file.
              It typically contains function and alias definitions.

       ERRNO  Integer value of the shell's errno  variable  --  indicates  the
              reason the last system call failed.

              Not implemented yet.

       EXECSHELL
              If  set,  this parameter is assumed to contain the shell that is
              to be used to execute commands that execve(2) fails  to  execute
              and which do not start with a `#! shell' sequence.

       FCEDIT The editor used by the fc command (see below).

       FPATH  Like  PATH,  but  used when an undefined function is executed to
              locate the file defining the function.  It is also searched when
              a  command  can't  be found using PATH.  See Functions below for
              more information.

       HISTFILE
              The name of the file used to store history.  When  assigned  to,
              history  is loaded from the specified file.  Also, several invo-
              cations of the shell running on the same machine will share his-
              tory if their HISTFILE parameters all point at the same file.
              NOTE:  if  HISTFILE isn't set, no history file is used.  This is
              different   from   the   original   Korn   shell,   which   uses
              $HOME/.sh_history;  in future, pdksh may also use a default his-
              tory file.

       HISTSIZE
              The number of commands normally stored for history, default 128.

       HOME   The  default  directory for the cd command and the value substi-
              tuted for an unqualified ~ (see Tilde Expansion below).

       IFS    Internal field separator, used during substitution  and  by  the
              read  command, to split values into distinct arguments; normally
              set to space, tab  and  newline.   See  Substitution  above  for
              details.
              Note:  this  parameter is not imported from the environment when
              the shell is started.

       KSH_VERSION
              The version of shell and the date the version was created (read-
              only).   See also the version commands in Emacs Editing Mode and
              Vi Editing Mode sections, below.

       LINENO The line number of the function or shell  script  that  is  cur-
              rently being executed.

       LINES  Set to the number of lines on the terminal or window.

              Not implemented yet.

       MAIL   If  set, the user will be informed of the arrival of mail in the
              named file.  This parameter is ignored if the MAILPATH parameter
              is set.

       MAILCHECK
              How  often,  in  seconds,  the  shell will check for mail in the
              file(s) specified by MAIL or MAILPATH.  If 0, the  shell  checks
              before each prompt.  The default is 600 (10 minutes).

       MAILPATH
              A list of files to be checked for mail.  The list is colon sepa-
              rated, and each file may be followed by a ? and a message to  be
              printed  if new mail has arrived.  Command, parameter and arith-
              metic substitution is performed on the message, and, during sub-
              stitution,  the parameter $_ contains the name of the file.  The
              default message is you have mail in $_.

       OLDPWD The previous working directory.  Unset if cd  has  not  success-
              fully  changed  directories  since  the shell started, or if the
              shell doesn't know where it is.

       OPTARG When using getopts,  it  contains  the  argument  for  a  parsed
              option, if it requires one.

       OPTIND The  index  of  the  last argument processed when using getopts.
              Assigning 1 to this parameter causes getopts  to  process  argu-
              ments from the beginning the next time it is invoked.

       PATH   A  colon  separated  list  of directories that are searched when
              looking for commands and .'d files.  An empty  string  resulting
              from  a  leading  or  trailing  colon, or two adjacent colons is
              treated as a `.', the current directory.

       POSIXLY_CORRECT
              If set, this parameter causes the posix option  to  be  enabled.
              See POSIX Mode below.

       PPID   The process ID of the shell's parent (readonly).

       PS1    PS1  is  the  primary prompt for interactive shells.  Parameter,
              command and arithmetic substitutions are  performed,  and  !  is
              replaced with the current command number (see fc command below).
              A literal ! can be put in the prompt by placing !! in PS1.  Note
              that  since  the command line editors try to figure out how long
              the prompt is (so they know  how  far  it  is  to  edge  of  the
              screen), escape codes in the prompt tend to mess things up.  You
              can tell the shell not  to  count  certain  sequences  (such  as
              escape codes) by prefixing your prompt with a non-printing char-
              acter (such as control-A) followed by a carriage return and then
              delimiting  the  escape  codes with this non-printing character.
              If you don't have any non-printing  characters,  you're  out  of
              luck...  BTW, don't blame me for this hack; it's in the original
              ksh.  Default is `$ ' for non-root users, `# ' for root..

       PS2    Secondary prompt string, by default `> ', used when  more  input
              is needed to complete a command.

       PS3    Prompt  used  by select statement when reading a menu selection.
              Default is `#? '.

       PS4    Used to prefix commands that are printed during execution  trac-
              ing  (see  set -x command below).  Parameter, command and arith-
              metic substitutions are performed before it is printed.  Default
              is `+ '.

       PWD    The  current  working  directory.   Maybe unset or null if shell
              doesn't know where it is.

       RANDOM A simple random number generator.  Every time RANDOM  is  refer-
              enced, it is assigned the next number in a random number series.
              The point in the series can be set by assigning a number to RAN-
              DOM (see rand(3)).

       REPLY  Default  parameter  for  the read command if no names are given.
              Also used in select loops to store the value that is  read  from
              standard input.

       SECONDS
              The number of seconds since the shell started or, if the parame-
              ter has been assigned an integer value, the  number  of  seconds
              since the assignment plus the value that was assigned.

       TMOUT  If  set to a positive integer in an interactive shell, it speci-
              fies the maximum number of seconds the shell will wait for input
              after  printing  the  primary  prompt  (PS1).   If  the  time is
              exceeded, the shell exits.

       TMPDIR The directory shell temporary files are  created  in.   If  this
              parameter is not set, or does not contain the absolute path of a
              writable directory, temporary files are created in /tmp.

       VISUAL If set, this parameter controls the command  line  editing  mode
              for interactive shells.  If the last component of the path spec-
              ified in this parameter contains the string vi, emacs or  gmacs,
              the  vi, emacs or gmacs (Gosling emacs) editing mode is enabled,
              respectively.

   Tilde Expansion
       Tilde expansion, which is done in parallel with parameter substitution,
       is done on words starting with an unquoted ~.  The characters following
       the tilde, up to the first /, if any, are assumed to be a  login  name.
       If the login name is empty, + or -, the value of the HOME, PWD, or OLD-
       PWD parameter is substituted, respectively.   Otherwise,  the  password
       file  is  searched for the login name, and the tilde expression is sub-
       stituted with the user's home directory.  If  the  login  name  is  not
       found  in the password file or if any quoting or parameter substitution
       occurs in the login name, no substitution is performed.

       In parameter assignments (those preceding  a  simple-command  or  those
       occurring  in  the  arguments of alias, export, readonly, and typeset),
       tilde expansion is done after any unquoted colon (:), and  login  names
       are also delimited by colons.

       The  home  directory  of previously expanded login names are cached and
       re-used.  The alias -d command may be used to list, change and  add  to
       this cache (e.g., `alias -d fac=/usr/local/facilities; cd ~fac/bin').

   Brace Expansion (alternation)
       Brace expressions, which take the form
              prefix{str1,...,strN}suffix
       are  expanded to N words, each of which is the concatenation of prefix,
       stri and suffix (e.g., `a{c,b{X,Y},d}e'  expands  to  four  word:  ace,
       abXe,  abYe,  and ade).  As noted in the example, brace expressions can
       be nested and the resulting words are not  sorted.   Brace  expressions
       must contain an unquoted comma (,) for expansion to occur (i.e., {} and
       {foo} are not expanded).  Brace expansion is carried out after  parame-
       ter substitution and before file name generation.

   File Name Patterns
       A  file  name  pattern is a word containing one or more unquoted ? or *
       characters or [..] sequences.  Once brace expansion has been performed,
       the  shell replaces file name patterns with the sorted names of all the
       files that match the pattern (if no  files  match,  the  word  is  left
       unchanged).  The pattern elements have the following meaning:

       ?      matches any single character.

       *      matches any sequence of characters.

       [..]   matches  any  of  the characters inside the brackets.  Ranges of
              characters can be specified by separating two characters by a -,
              e.g.,  [a0-9]  matches  the  letter a or any digit.  In order to
              represent itself, a - must either be quoted or the first or last
              character  in the character list.  Similarly, a ] must be quoted
              or the first character in the list if  it  is  represent  itself
              instead  of  the  end  of the list.  Also, a !  appearing at the
              start of the list has special meaning (see below), so to  repre-
              sent itself it must be quoted or appear later in the list.

       [!..]  like [..], except it matches any character not inside the brack-
              ets.

       *(pattern| ... |pattern)
              matches any string of  characters  that  matches  zero  or  more
              occurrences  of  the  specified  patterns.  Example: the pattern
              *(foo|bar) matches the strings `',  `foo',  `bar',  `foobarfoo',
              etc..

       +(pattern| ... |pattern)
              matches any string of characters that matches one or more occur-
              rences  of  the  specified  patterns.   Example:   the   pattern
              +(foo|bar)  matches the strings `foo', `bar', `foobarfoo', etc..

       ?(pattern| ... |pattern)
              matches the empty string or a string that  matches  one  of  the
              specified   patterns.   Example:  the  pattern  ?(foo|bar)  only
              matches the strings `', `foo' and `bar'.

       @(pattern| ... |pattern)
              matches a string that matches one  of  the  specified  patterns.
              Example:  the  pattern @(foo|bar) only matches the strings `foo'
              and `bar'.

       !(pattern| ... |pattern)
              matches any string that does not match one of the specified pat-
              terns.   Examples:  the  pattern  !(foo|bar) matches all strings
              except `foo' and `bar'; the pattern !(*) matches no strings; the
              pattern !(?)* matches all strings (think about it).

       Note that pdksh currently never matches . and .., but the original ksh,
       Bourne sh and bash do, so this may have to change (too bad).

       Note that none of the above pattern elements match either a period  (.)
       at the start of a file name or a slash (/), even if they are explicitly
       used in a [..] sequence; also, the names . and ..  are  never  matched,
       even by the pattern .*.

       If  the  markdirs  option is set, any directories that result from file
       name generation are marked with a trailing /.

       The POSIX character classes (i.e., [:class-name:] inside a [..] expres-
       sion) are not yet implemented.

   Input/Output Redirection
       When  a  command  is  executed, its standard input, standard output and
       standard error (file descriptors 0, 1 and 2, respectively) are normally
       inherited  from  the  shell.   Three exceptions to this are commands in
       pipelines, for which standard input and/or standard  output  are  those
       set  up by the pipeline, asynchronous commands created when job control
       is disabled, for which standard input  is  initially  set  to  be  from
       /dev/null,  and  commands  for  which any of the following redirections
       have been specified:

       > file standard output is redirected to file.  If file does not  exist,
              it  is  created;  if  it  does  exist, is a regular file and the
              noclobber option is set, an error occurs, otherwise the file  is
              truncated.   Note  that  this  means the command cmd < foo > foo
              will open foo for reading and then truncate it when it opens  it
              for writing, before cmd gets a chance to actually read foo.

       >| file
              same  as  >, except the file is truncated, even if the noclobber
              option is set.

       >> file
              same as >, except the file  an  existing  file  is  appended  to
              instead  of being truncated.  Also, the file is opened in append
              mode, so writes always go to the end of the file (see  open(2)).

       < file standard  input  is  redirected  from  file, which is opened for
              reading.

       <> file
              same as <, except the file is opened for reading and writing.

       << marker
              after reading the command line containing this kind of redirect-
              ion  (called  a  here document), the shell copies lines from the
              command source into a  temporary  file  until  a  line  matching
              marker is read.  When the command is executed, standard input is
              redirected from the  temporary  file.   If  marker  contains  no
              quoted  characters,  the contents of the temporary file are pro-
              cessed as if enclosed in double quotes each time the command  is
              executed, so parameter, command and arithmetic substitutions are
              performed, along with backslash (\) escapes  for  $,  `,  \  and
              \newline.   If multiple here documents are used on the same com-
              mand line, they are saved in order.

       <<- marker
              same as <<, except leading tabs are stripped from lines  in  the
              here document.

       <& fd  standard input is duplicated from file descriptor fd.  fd can be
              a single digit,  indicating  the  number  of  an  existing  file
              descriptor, the letter p, indicating the file descriptor associ-
              ated with the output of the current co-process, or the character
              -, indicating standard input is to be closed.

       >& fd  same as <&, except the operation is done on standard output.

       In  any  of  the  above redirections, the file descriptor that is redi-
       rected (i.e., standard input or  standard  output)  can  be  explicitly
       given  by  preceding  the  redirection with a single digit.  Parameter,
       command and arithmetic substitutions, tilde substitutions and  (if  the
       shell  is  interactive)  file  name generation are all performed on the
       file, marker and fd arguments of redirections.  Note however, that  the
       results  of  any file name generation are only used if a single file is
       matched; if multiple files match, the word  with  the  unexpanded  file
       name  generation  characters  is used.  Note that in restricted shells,
       redirections which can create files cannot be used.

       For simple-commands, redirections may appear anywhere in  the  command,
       for  compound-commands  (if  statements,  etc.),  any redirections must
       appear at the end.  Redirections are processed after pipelines are cre-
       ated and in the order they are given, so
              cat /foo/bar 2>&1 > /dev/null | cat -n
       will print an error with a line number prepended to it.

   Arithmetic Expressions
       Integer arithmetic expressions can be used with the let command, inside
       $((..)) expressions, inside array  references  (e.g.,  name[expr]),  as
       numeric  arguments  to the test command, and as the value of an assign-
       ment to an integer parameter.

       Expression may contain alpha-numeric parameter identifiers, array  ref-
       erences, and integer constants and may be combined with the following C
       operators (listed and grouped in increasing order of precedence).

       Unary operators:
              + - ! ~ ++ --

       Binary operators:
              ,
              = *= /= %= += -= <<= >>= &= ^= |=
              ||
              &&
              |
              ^
              &
              == !=
              < <= >= >
              << >>
              + -
              * / %

       Ternary operator:
              ?: (precedence is immediately higher than assignment)

       Grouping operators:
              ( )

       Integer constants may be specified with arbitrary bases using the nota-
       tion  base#number, where base is a decimal integer specifying the base,
       and number is a number in the specified base.

       The operators are evaluated as follows:

              unary +
                     result is the argument (included for completeness).

              unary -
                     negation.

              !      logical not; the result is 1 if argument is  zero,  0  if
                     not.

              ~      arithmetic (bit-wise) not.

              ++     increment;  must be applied to a parameter (not a literal
                     or other expression) - the parameter is incremented by 1.
                     When  used as a prefix operator, the result is the incre-
                     mented value of the parameter, when  used  as  a  postfix
                     operator, the result is the original value of the parame-
                     ter.

              --     similar to ++, except the parameter is decremented by  1.

              ,      separates  two arithmetic expressions; the left hand side
                     is evaluated first, then the right.  The result is  value
                     of the expression on the right hand side.

              =      assignment;  variable  on the left is set to the value on
                     the right.

              *= /= %= += -= <<= >>= &= ^= |=
                     assignment operators; <var> <op>= <expr> is the  same  as
                     <var> = <var> <op> ( <expr> ).

              ||     logical  or;  the  result is 1 if either argument is non-
                     zero, 0 if not.  The right argument is evaluated only  if
                     the left argument is zero.

              &&     logical  and;  the result is 1 if both arguments are non-
                     zero, 0 if not.  The right argument is evaluated only  if
                     the left argument is non-zero.

              |      arithmetic (bit-wise) or.

              ^      arithmetic (bit-wise) exclusive-or.

              &      arithmetic (bit-wise) and.

              ==     equal;  the result is 1 if both arguments are equal, 0 if
                     not.

              !=     not equal; the result is 0 if both arguments are equal, 1
                     if not.

              <      less  than;  the result is 1 if the left argument is less
                     than the right, 0 if not.

              <= >= >
                     less than or equal, greater than or equal, greater  than.
                     See <.

              << >>  shift  left (right); the result is the left argument with
                     its bits shifted left (right) by the amount given in  the
                     right argument.

              + - * /
                     addition, subtraction, multiplication, and division.

              %      remainder; the result is the remainder of the division of
                     the left argument by the right.  The sign of  the  result
                     is unspecified if either argument is negative.

              <arg1> ? <arg2> : <arg3>
                     if  <arg1>  is  non-zero, the result is <arg2>, otherwise
                     <arg3>.

   Co-Processes
       A co-process, which is a pipeline created with the |& operator,  is  an
       asynchronous  process that the shell can both write to (using print -p)
       and read from (using read -p).  The input and output of the  co-process
       can  also  be manipulated using >&p and <&p redirections, respectively.
       Once a co-process has been started, another can't be started until  the
       co-process  exits,  or  until  the co-process input has been redirected
       using an exec n>&p redirection.  If a co-process's input is  redirected
       in  this  way,  the next co-process to be started will share the output
       with the first co-process, unless the output of the initial  co-process
       has been redirected using an exec n<&p redirection.

       Some notes concerning co-processes:
         o    the  only  way  to close the co-process input (so the co-process
              reads an end-of-file) is to redirect the  input  to  a  numbered
              file  descriptor and then close that file descriptor (e.g., exec
              3>&p;exec 3>&-).
         o    in order for co-processes to share a common  output,  the  shell
              must keep the write portion of the output pipe open.  This means
              that end of file will not be  detected  until  all  co-processes
              sharing  the  co-process output have exited (when they all exit,
              the shell closes its copy of the pipe).  This can be avoided  by
              redirecting  the  output  to a numbered file descriptor (as this
              also causes the shell to close its copy).  Note that this behav-
              iour  is  slightly  different from the original Korn shell which
              closes its copy of the write portion of the co-processes' output
              when  the  most recently started co-process (instead of when all
              sharing co-processes) exits.
         o    print -p will ignore SIGPIPE signals during writes if the signal
              is not being trapped or ignored; the same is not true if the co-
              process input has been duplicated to another file descriptor and
              print -un is used.

   Functions
       Functions  are  defined using either Korn shell function name syntax or
       the Bourne/POSIX shell name() syntax  (see  below  for  the  difference
       between  the two forms).  Functions are like .-scripts in that they are
       executed in the current environment, however, unlike  .-scripts,  shell
       arguments  (i.e.,  positional  parameters,  $1, etc.) are never visible
       inside them.  When the shell is determining the location of a  command,
       functions are searched after special built-in commands, and before reg-
       ular and non-regular built-ins, and before the PATH is searched.

       An existing function may be deleted using unset  -f  function-name.   A
       list  of  functions  can  be obtained using typeset +f and the function
       definitions can be listed using typeset  -f.   autoload  (which  is  an
       alias  for typeset -fu) may be used to create undefined functions; when
       an undefined function is executed, the shell searches the  path  speci-
       fied  in the FPATH parameter for a file with the same name as the func-
       tion, which, if found is read and executed.   If  after  executing  the
       file,  the  named function is found to be defined, the function is exe-
       cuted, otherwise, the normal command search  is  continued  (i.e.,  the
       shell searches the regular built-in command table and PATH).  Note that
       if a command is not found using PATH, an attempt is made to autoload  a
       function  using  FPATH (this is an undocumented feature of the original
       Korn shell).

       Functions can have two attributes, trace and export, which can  be  set
       with typeset -ft and typeset -fx, respectively.  When a traced function
       is executed, the shell's xtrace option is turned on for  the  functions
       duration,  otherwise  the  xtrace  option  is  turned  off.  The export
       attribute of functions is currently not used.   In  the  original  Korn
       shell,  exported  functions  are visible to shell scripts that are exe-
       cuted.

       Since functions are executed in the current shell environment,  parame-
       ter  assignments  made  inside functions are visible after the function
       completes.  If this is not the desired effect, the typeset command  can
       be  used inside a function to create a local parameter.  Note that spe-
       cial parameters (e.g., $$, $!) can't be scoped in this way.

       The exit status of a function is that of the last command  executed  in
       the  function.   A function can be made to finish immediately using the
       return command; this may also be used to explicitly  specify  the  exit
       status.

       Functions  defined  with the function reserved word are treated differ-
       ently in the following ways from functions defined with  the  ()  nota-
       tion:
         o    the  $0  parameter  is  set to the name of the function (Bourne-
              style functions leave $0 untouched).
         o    parameter assignments preceding function calls are not  kept  in
              the  shell  environment  (executing  Bourne-style functions will
              keep assignments).
         o    OPTIND is saved/reset and restored on entry and  exit  from  the
              function so getopts can be used properly both inside and outside
              the function (Bourne-style functions leave OPTIND untouched,  so
              using  getopts  inside  a function interferes with using getopts
              outside the function).  In the future, the following differences
              will also be added:
         o    A  separate trap/signal environment will be used during the exe-
              cution of functions.  This will mean that  traps  set  inside  a
              function  will not affect the shell's traps and signals that are
              not ignored in the shell (but may be trapped)  will  have  their
              default effect in a function.
         o    The  EXIT trap, if set in a function, will be executed after the
              function returns.

   POSIX Mode
       The shell is intended to be POSIX compliant, however,  in  some  cases,
       POSIX behaviour is contrary either to the original Korn shell behaviour
       or to user convenience.  How the shell behaves in these cases is deter-
       mined  by  the state of the posix option (set -o posix) -- if it is on,
       the POSIX behaviour is followed, otherwise it is not.  The posix option
       is  set  automatically when the shell starts up if the environment con-
       tains the POSIXLY_CORRECT parameter.  (The shell can also  be  compiled
       so  that  it  is  in POSIX mode by default, however this is usually not
       desirable).

       The following is a list of things that are affected by the state of the
       posix option:
         o    kill  -l  output:  in  posix mode, signal names are listed one a
              single line;  in  non-posix  mode,  signal  numbers,  names  and
              descriptions  are  printed  in columns.  In future, a new option
              (-v perhaps) will be added to distinguish the two behaviours.
         o    fg exit status: in posix mode, the exit status is 0 if no errors
              occur;  in  non-posix  mode, the exit status is that of the last
              foregrounded job.
         o    eval exit status: if eval gets to see an  empty  command  (e.g.,
              eval  "`false`"),  its  exit status in posix mode will be 0.  In
              non-posix mode, it will be the exit status of the  last  command
              substitution that was done in the processing of the arguments to
              eval (or 0 if there were no command substitutions).
         o    getopts: in posix mode, options must start with  a  -;  in  non-
              posix mode, options can start with either - or +.
         o    brace  expansion  (also  known  as  alternation): in posix mode,
              brace expansion is disabled; in non-posix mode, brace  expansion
              enabled.  Note that set -o posix (or setting the POSIXLY_CORRECT
              parameter) automatically turns the braceexpand option off,  how-
              ever it can be explicitly turned on later.
         o    set  -: in posix mode, this does not clear the verbose or xtrace
              options; in non-posix mode, it does.
         o    set exit status: in posix mode, the exit status of set is  0  if
              there  are no errors; in non-posix mode, the exit status is that
              of any command substitutions performed  in  generating  the  set
              command.   For  example,  `set  -- `false`; echo $?' prints 0 in
              posix mode, 1 in non-posix mode.  This construct is used in most
              shell scripts that use the old getopt(1) command.
         o    argument  expansion of alias, export, readonly, and typeset com-
              mands: in posix mode, normal argument expansion  done;  in  non-
              posix  mode,  field splitting, file globing, brace expansion and
              (normal) tilde expansion are turned off,  and  assignment  tilde
              expansion is turned on.
         o    signal specification: in posix mode, signals can be specified as
              digits only if signal numbers match POSIX values  (i.e.,  HUP=1,
              INT=2,  QUIT=3,  ABRT=6,  KILL=9, ALRM=14, and TERM=15); in non-
              posix mode, signals can be always digits.
         o    alias expansion: in posix mode, alias expansion is only  carried
              out  when reading command words; in non-posix mode, alias expan-
              sion is carried out on any word following an alias that ended in
              a space.  For example, the following for loop
              alias a='for ' i='j'
              a i in 1 2; do echo i=$i j=$j; done
       uses parameter i in posix mode, j in non-posix mode.
         o    test:  in posix mode, the expression "-t" (preceded by some num-
              ber of "!" arguments) is always true as it is a non-zero  length
              string;  in  non-posix  mode, it tests if file descriptor 1 is a
              tty (i.e., the fd argument to the -t test may be  left  out  and
              defaults to 1).

   Command Execution
       After  evaluation of command line arguments, redirections and parameter
       assignments, the type of command is determined: a special  built-in,  a
       function,  a  regular  built-in  or the name of a file to execute found
       using the PATH parameter.  The checks are  made  in  the  above  order.
       Special  built-in  commands differ from other commands in that the PATH
       parameter is not used to find them, an error during their execution can
       cause  a  non-interactive  shell to exit and parameter assignments that
       are specified before the command are kept after the command  completes.
       Just to confuse things, if the posix option is turned off (see set com-
       mand below) some special commands are very special  in  that  no  field
       splitting,  file  globing,  brace expansion nor tilde expansion is per-
       formed on arguments that look like assignments.  Regular built-in  com-
       mands are different only in that the PATH parameter is not used to find
       them.

       The original ksh and POSIX differ somewhat in which commands  are  con-
       sidered special or regular:

       POSIX special commands

              .          continue   exit       return     trap
              :          eval       export     set        unset
              break      exec       readonly   shift

       Additional ksh special commands

              builtin    times      typeset

       Very special commands (non-posix mode)


              alias      readonly   set        typeset

       POSIX regular commands

              alias      command    fg         kill       umask
              bg         false      getopts    read       unalias
              cd         fc         jobs       true       wait

       Additional ksh regular commands

              [          let        pwd        ulimit
              echo       print      test       whence

       In  the  future, the additional ksh special and regular commands may be
       treated differently from the POSIX special and regular commands.

       Once the type of the command has  been  determined,  any  command  line
       parameter  assignments  are  performed and exported for the duration of
       the command.

       The following describes the special and regular built-in commands:

       . file [arg1 ...]
              Execute the commands in file in the  current  environment.   The
              file  is  searched for in the directories of PATH.  If arguments
              are given, the positional parameters may be used to access  them
              while  file  is  being executed.  If no arguments are given, the
              positional parameters are those of the environment  the  command
              is used in.

       : [ ... ]
              The null command.  Exit status is set to zero.

       alias [ -d | +-t [-r] ] [+-px] [+-] [name1[=value1] ...]
              Without  arguments, alias lists all aliases.  For any name with-
              out a value, the existing alias is  listed.   Any  name  with  a
              value defines an alias (see Aliases above).

              When  listing  aliases,  one  of  two formats is used: normally,
              aliases are listed as name=value,  where  value  is  quoted;  if
              options were preceded with + or a lone + is given on the command
              line, only name is printed.  In addition, if the  -p  option  is
              used, each alias is prefixed with the string "alias ".

              The -x option sets (+x clears) the export attribute of an alias,
              or, if no names are given, lists the  aliases  with  the  export
              attribute (exporting an alias has no affect).

              The   -t  option  indicates  that  tracked  aliases  are  to  be
              listed/set (values specified on the command line are ignored for
              tracked  aliases).   The  -r  option  indicates that all tracked
              aliases are to be reset.

              The -d causes directory aliases, which are used in tilde  expan-
              sion, to be listed or set (see Tilde Expansion above).

       bg [job ...]
              Resume  the  specified  stopped job(s) in the background.  If no
              jobs are specified, %+ is assumed.  This command is only  avail-
              able  on  systems  which  support  job control.  See Job Control
              below for more information.

       bind [-m] [key[=editing-command] ...]
              Set  or  view  the  current  emacs  command  editing  key  bind-
              ings/macros.   See  Emacs  Editing  Mode  below  for  a complete
              description.

       break [level]
              break exits the levelth inner most for, select, until, or  while
              loop.  level defaults to 1.

       builtin command [arg1 ...]
              Execute the built-in command command.

       cd [-LP] [dir]
              Set  the  working  directory to dir.  If the parameter CDPATH is
              set, it lists directories to search in for dir.  An empty  entry
              in the CDPATH entry means the current directory.  If a non-empty
              directory from CDPATH  is  used,  the  resulting  full  path  is
              printed  to standard output.  If dir is missing, the home direc-
              tory $HOME is used.  If dir is -, the previous working directory
              is  used (see OLDPWD parameter).  If -L option (logical path) is
              used or if the physical option (see  set  command  below)  isn't
              set,  references  to .. in dir are relative to the path used get
              to the directory.  If -P option (physical path) is  used  or  if
              the  physical  option  is  set, .. is relative to the filesystem
              directory tree.  The PWD and OLDPWD parameters  are  updated  to
              reflect the current and old wording directory, respectively.

       cd [-LP] old new
              The  string new is substituted for old in the current directory,
              and the shell attempts to change to the new directory.

       command [-pvV] cmd [arg1 ...]
              If neither the -v nor -V options  are  given,  cmd  is  executed
              exactly  as  if  the  command  had  not been specified, with two
              exceptions: first, cmd cannot be a shell function,  and  second,
              special  built-in  commands  lose their specialness (i.e., redi-
              rection and utility errors do not cause the shell to  exit,  and
              command  assignments  are  not  permanent).  If the -p option is
              given, a default search path is  used  instead  of  the  current
              value  of  PATH  (the actual value of the default path is system
              dependent: on POSIXish systems, it is the value returned by
                                      getconf CS_PATH
              ).

              If the -v option is given, instead of executing cmd, information
              about  what would be executed is given (and the same is done for
              arg1 ...): for special and regular built-in commands  and  func-
              tions,  their  names  are simply printed, for aliases, a command
              that defines them is printed, and for commands found by  search-
              ing the PATH parameter, the full path of the command is printed.
              If no command is found, (i.e., the path search  fails),  nothing
              is  printed  and  command  exits with a non-zero status.  The -V
              option is like the -v option, except it is more verbose.

       continue [levels]
              continue jumps to the beginning of the levelth inner  most  for,
              select, until, or while loop.  level defaults to 1.

       echo [-neE] [arg ...]
              Prints  its  arguments  (separated by spaces) followed by a new-
              line, to standard out.  The newline is suppressed if any of  the
              arguments  contain the backslash sequence \c.  See print command
              below for a list of other backslash sequences  that  are  recog-
              nized.

              The  options  are  provided  for  compatibility  with  BSD shell
              scripts: -n suppresses the trailing newline,  -e  enables  back-
              slash interpretation (a no-op, since this is normally done), and
              -E suppresses backslash interpretation.

       eval command ...
              The arguments are concatenated (with  spaces  between  them)  to
              form a single string which the shell then parses and executes in
              the current environment.

       exec [command [arg ...]]
              The command is executed without  forking,  replacing  the  shell
              process.

              If  no  arguments are given, any IO redirection is permanent and
              the shell is not replaced.  Any file descriptors greater than  2
              which are opened or dup(2)-ed in this way are not made available
              to other executed commands (i.e., commands that are not built-in
              to the shell).  Note that the Bourne shell differs here: it does
              pass these file descriptors on.

       exit [status]
              The shell exits with the specified exit status.   If  status  is
              not  specified,  the  exit  status is the current value of the ?
              parameter.

       export [-p] [parameter[=value]] ...
              Sets the export attribute of  the  named  parameters.   Exported
              parameters  are  passed in the environment to executed commands.
              If values are specified, the named parameters also assigned.

              If no parameters are specified, the names of all parameters with
              the  export  attribute  are  printed one per line, unless the -p
              option is used, in  which  case  export  commands  defining  all
              exported parameters, including their values, are printed.

       false  A command that exits with a non-zero status.

       fc [-e editor | -l [-n]] [-r] [first [last]]
              first  and  last select commands from the history.  Commands can
              be selected by history number, or a string specifying  the  most
              recent  command  starting with that string.  The -l option lists
              the command on stdout, and -n inhibits the default command  num-
              bers.   The  -r  option reverses the order of the list.  Without
              -l, the selected commands are edited  by  the  editor  specified
              with  the -e option, or if no -e is specified, the editor speci-
              fied by the FCEDIT parameter (if  this  parameter  is  not  set,
              /bin/ed is used), and then executed by the shell.

       fc [-e - | -s] [-g] [old=new] [prefix]
              Re-execute   the  selected  command  (the  previous  command  by
              default) after performing the optional substitution of old  with
              new.   If  -g  is specified, all occurrences of old are replaced
              with new.  This command is usually accessed with the  predefined
              alias r='fc -e -'.

       fg [job ...]
              Resume  the  specified job(s) in the foreground.  If no jobs are
              specified, %+ is assumed.  This command  is  only  available  on
              systems  which  support  job control.  See Job Control below for
              more information.

       getopts optstring name [arg ...]
              getopts is used by shell procedures to parse the specified argu-
              ments  (or positional parameters, if no arguments are given) and
              to check for legal options.  optstring contains the option  let-
              ters that getopts is to recognize.  If a letter is followed by a
              colon, the option is expected to have an argument.  Options that
              do  not  take arguments may be grouped in a single argument.  If
              an option takes an argument and the option character is not  the
              last  character of the argument it is found in, the remainder of
              the argument is taken to be the  option's  argument,  otherwise,
              the next argument is the option's argument.

              Each  time  getopts is invoked, it places the next option in the
              shell parameter name and the index of the next  argument  to  be
              processed  in  the  shell  parameter  OPTIND.  If the option was
              introduced with a +, the option placed in name is prefixed  with
              a  +.  When an option requires an argument, getopts places it in
              the shell parameter OPTARG.  When an illegal option or a missing
              option  argument  is  encountered  a question mark or a colon is
              placed in name (indicating an illegal option  or  missing  argu-
              ment,  respectively)  and  OPTARG is set to the option character
              that caused the problem.  An error message is  also  printed  to
              standard error if optstring does not begin with a colon.

              When the end of the options is encountered, getopts exits with a
              non-zero exit status.  Options end  at  the  first  (non-option)
              argument  that does not start with a -, or when a -- argument is
              encountered.

              Option parsing can be reset by setting OPTIND to 1 (this is done
              automatically  whenever  the  shell  or  a  shell  procedure  is
              invoked).

              Warning: Changing the value of the shell parameter OPTIND  to  a
              value other than 1, or parsing different sets of arguments with-
              out resetting OPTIND may lead to unexpected results.

       hash [-r] [name ...]
              Without arguments, any hashed executable command  pathnames  are
              listed.   The -r option causes all hashed commands to be removed
              from the hash table.  Each name is searched as  if  it  where  a
              command  name and added to the hash table if it is an executable
              command.

       jobs [-lpn] [job ...]
              Display information about the specified jobs;  if  no  jobs  are
              specified,  all jobs are displayed.  The -n option causes infor-
              mation to be displayed only for jobs  that  have  changed  state
              since  the  last  notification.   If  the -l option is used, the
              process-id of each process in a job  is  also  listed.   The  -p
              option  causes only the process group of each job to be printed.
              See Job Control below for the format of job  and  the  displayed
              job.

       kill [-s signame | -signum | -signame ] { job | pid | -pgrp } ...
              Send the specified signal to the specified jobs, process ids, or
              process groups.  If no signal is specified, the signal  TERM  is
              sent.   If  a  job is specified, the signal is sent to the job's
              process group.  See Job Control below for the format of job.

       kill -l [exit-status ...]
              Print the name of the signal that killed a process which  exited
              with  the  specified  exit-statuses.  If no arguments are speci-
              fied, a list of all the  signals,  their  numbers  and  a  short
              description of them are printed.

       let [expression ...]
              Each  expression is evaluated, see Arithmetic Expressions above.
              If all expressions are successfully evaluated, the  exit  status
              is  0  (1)  if the last expression evaluated to non-zero (zero).
              If an error occurs  during  the  parsing  or  evaluation  of  an
              expression,  the  exit  status is greater than 1.  Since expres-
              sions may need to be quoted, (( expr )) is syntactic  sugar  for
              let "expr".

       print [-nprsun | -R [-en]] [argument ...]
              Print  prints its arguments on the standard output, separated by
              spaces, and terminated with a newline.  The -n option suppresses
              the  newline.   By  default,  certain  C escapes are translated.
              These include \b, \f, \n, \r, \t, \v, and \0### (# is  an  octal
              digit, of which there may be 0 to 3).  \c is equivalent to using
              the -n option.  \ expansion may be inhibited with the -r option.
              The  -s  option  prints  to the history file instead of standard
              output, the -u option prints to file descriptor n (n defaults to
              1  if  omitted), and the -p option prints to the co-process (see
              Co-Processes above).

              The -R option is used to emulate, to some degree, the  BSD  echo
              command, which does not process \ sequences unless the -e option
              is given.  As above, the -n option suppresses the trailing  new-
              line.

       pwd [-LP]
              Print the present working directory.  If -L option is used or if
              the physical option (see set command below) isn't set, the logi-
              cal  path  is  printed (i.e., the path used to cd to the current
              directory).  If -P option (physical path)  is  used  or  if  the
              physical  option is set, the path determined from the filesystem
              (by following ..  directories to the root directory) is printed.

       read [-prsun] [parameter ...]
              Reads  a  line  of  input from standard input, separate the line
              into fields using the IFS parameter  (see  Substitution  above),
              and assign each field to the specified parameters.  If there are
              more parameters than fields, the extra  parameters  are  set  to
              null,  or  alternatively,  if there are more fields than parame-
              ters, the  last  parameter  is  assigned  the  remaining  fields
              (inclusive  of  any  separating  spaces).   If no parameters are
              specified, the REPLY parameter is used.  If the input line  ends
              in a backslash and the -r option was not used, the backslash and
              newline are stripped and more input is read.   If  no  input  is
              read, read exits with a non-zero status.

              The  first  parameter  may  have  a  question  mark and a string
              appended to it, in which case the string is  used  as  a  prompt
              (printed  to  standard  error  before  any input is read) if the
              input is a tty (e.g., read nfoo?'number of foos: ').

              The -un and -p options cause input to be read from file descrip-
              tor n or the current co-process (see Co-Processes above for com-
              ments on this), respectively.  If the -s option is  used,  input
              is saved to the history file.

       readonly [-p] [parameter[=value]] ...
              Sets  the readonly attribute of the named parameters.  If values
              are given,  parameters  are  set  to  them  before  setting  the
              attribute.   Once  a  parameter  is  made readonly, it cannot be
              unset and its value cannot be changed.

              If no parameters are specified, the names of all parameters with
              the  readonly  attribute are printed one per line, unless the -p
              option is used, in which case  readonly  commands  defining  all
              readonly parameters, including their values, are printed.

       return [status]
              Returns  from  a  function or . script, with exit status status.
              If no status is given, the exit status of the last executed com-
              mand is used.  If used outside of a function or . script, it has
              the same effect as exit.  Note that pdksh  treats  both  profile
              and  $ENV files as . scripts, while the original Korn shell only
              treats profiles as . scripts.

       set [+-abCefhkmnpsuvxX] [+-o [option]] [+-A name] [--] [arg ...]
              The set command can be used  to  set  (-)  or  clear  (+)  shell
              options,  set the positional parameters, or set an array parame-
              ter.  Options can be changed using the +-o option syntax,  where
              option is the long name of an option, or using the +-letter syn-
              tax, where letter is the option's single letter  name  (not  all
              options  have  a single letter name).  The following table lists
              both option letters (if they exist) and long names along with  a
              description of what the option does.










               -A                               Sets the elements of the array
                                                parameter name to arg ...;  If
                                                -A is used, the array is reset
                                                (i.e., emptied) first;  if  +A
                                                is  used, the first N elements
                                                are set (where N is the number
                                                of  args),  the  rest are left
                                                untouched.
               -a         allexport             all new parameters are created
                                                with the export attribute
               -b         notify                Print  job  notification  mes-
                                                sages asynchronously,  instead
                                                of  just  before  the  prompt.
                                                Only used if  job  control  is
                                                enabled (-m).
               -C         noclobber             Prevent   >  redirection  from
                                                overwriting existing files (>|
                                                must be used to force an over-
                                                write).
               -e         errexit               Exit (after executing the  ERR
                                                trap)  as  soon  as  an  error
                                                occurs  or  a  command   fails
                                                (i.e.,  exits  with a non-zero
                                                status).  This does not  apply
                                                to  commands whose exit status
                                                is  explicitly  tested  by   a
                                                shell  construct  such  as if,
                                                until, while, && or ||  state-
                                                ments.
               -f         noglob                Do  not  expand file name pat-
                                                terns.
               -h         trackall              Create tracked aliases for all
                                                executed commands (see Aliases
                                                above).   On  by  default  for
                                                non-interactive shells.
               -i         interactive           Enable interactive mode - this
                                                can only be set/unset when the
                                                shell is invoked.
               -k         keyword               Parameter assignments are rec-
                                                ognized anywhere in a command.
               -l         login                 The  shell  is a login shell -
                                                this  can  only  be  set/unset
                                                when the shell is invoked (see
                                                Shell Startup above).
               -m         monitor               Enable  job  control  (default
                                                for interactive shells).
               -n         noexec                Do  not execute any commands -
                                                useful for checking the syntax
                                                of  scripts (ignored if inter-
                                                active).
               -p         privileged            Set automatically if, when the
                                                shell  starts, the real uid or
                                                gid does not match the  effec-
                                                tive uid or gid, respectively.
                                                See Shell Startup above for  a
                                                description   of   what   this
                                                means.
               -r         restricted            Enable restricted mode -- this
                                                option  can  only be used when
                                                the  shell  is  invoked.   See
                                                Shell   Startup  above  for  a
                                                description   of   what   this
                                                means.







               -s         stdin                 If  used  when  the  shell  is
                                                invoked,  commands  are   read
                                                from   standard   input.   Set
                                                automatically if the shell  is
                                                invoked with no arguments.

                                                When  -s  is  used  in the set
                                                command, it causes the  speci-
                                                fied  arguments  to  be sorted
                                                before assigning them  to  the
                                                positional  parameters  (or to
                                                array name, if -A is used).
               -u         nounset               Referencing of an unset param-
                                                eter  is  treated as an error,
                                                unless one of the -,  +  or  =
                                                modifiers is used.
               -v         verbose               Write  shell input to standard
                                                error as it is read.
               -x         xtrace                Print commands  and  parameter
                                                assignments when they are exe-
                                                cuted, preceded by  the  value
                                                of PS4.
               -X         markdirs              Mark directories with a trail-
                                                ing / during file name genera-
                                                tion.
                          bgnice                Background  jobs  are run with
                                                lower priority.
                          braceexpand           Enable brace  expansion  (aka,
                                                alternation).
                          emacs                 Enable  BRL emacs-like command
                                                line   editing    (interactive
                                                shells  only); see Emacs Edit-
                                                ing Mode.
                          emacs-usemeta         In emacs command-line editing,
                                                use  the  8th bit as meta (^[)
                                                prefix.  This is  the  default
                                                if  LC_CTYPE is unset or POSIX
                                                respectively C.  8
                          gmacs                 Enable   gmacs-like   (Gosling
                                                emacs)  command  line  editing
                                                (interactive   shells   only);
                                                currently  identical  to emacs
                                                editing except that  transpose
                                                (^T)   acts  slightly  differ-
                                                ently.
                          ignoreeof             The shell  will  not  (easily)
                                                exit  on  when  end-of-file is
                                                read, exit must be  used.   To
                                                avoid   infinite   loops,  the
                                                shell will exit if eof is read
                                                13 times in a row.
                          nohup                 Do  not kill running jobs with
                                                a  HUP  signal  when  a  login
                                                shell  exists.   Currently set
                                                by  default,  but  this   will
                                                change  in  the  future  to be
                                                compatible with  the  original
                                                Korn shell (which doesn't have
                                                this option, but does send the
                                                HUP signal).
                          nolog                 No  effect  -  in the original
                                                Korn  shell,   this   prevents
                                                function    definitions   from
                                                being stored  in  the  history
                                                file.





                          physical              Causes the cd and pwd commands
                                                to use `physical'  (i.e.,  the
                                                filesystem's)  ..  directories
                                                instead of `logical'  directo-
                                                ries (i.e.,  the shell handles
                                                .., which allows the  user  to
                                                be  oblivious of symlink links
                                                to  directories).   Clear   by
                                                default.   Note  that  setting
                                                this option  does  not  effect
                                                the  current  value of the PWD
                                                parameter; only the cd command
                                                changes  PWD.   See the cd and
                                                pwd commands  above  for  more
                                                details.
                          posix                 Enable  posix mode.  See POSIX
                                                Mode above.
                          vi                    Enable  vi-like  command  line
                                                editing   (interactive  shells
                                                only).
                          viraw                 No effect -  in  the  original
                                                Korn  shell,  unless viraw was
                                                set, the vi command line  mode
                                                would  let  the  tty driver do
                                                the work until  ESC  (^[)  was
                                                entered.   pdksh  is always in
                                                viraw mode.
                          vi-esccomplete        In vi command line editing, do
                                                command / file name completion
                                                when escape (^[) is entered in
                                                command mode.
                          vi-show8              Prefix   characters  with  the
                                                eighth bit set with `M-'.   If
                                                this  option is not set, char-
                                                acters in  the  range  128-160
                                                are  printed  as is, which may
                                                cause problems.
                          vi-tabcomplete        In vi command line editing, do
                                                command / file name completion
                                                when tab (^I)  is  entered  in
                                                insert   mode.   This  is  the
                                                default.

              These options can also be used upon  invocation  of  the  shell.
              The  current  set  of  options (with single letter names) can be
              found in the parameter -.  set -o with no option name will  list
              all the options and whether each is on or off; set +o will print
              the long names of all options that are currently on.

              Remaining arguments, if any, are positional parameters  and  are
              assigned,  in  order,  to the positional parameters (i.e., 1, 2,
              etc.).  If options are ended with -- and there are no  remaining
              arguments, all positional parameters are cleared.  If no options
              or arguments are  given,  then  the  values  of  all  names  are
              printed.   For  unknown  historical  reasons, a lone - option is
              treated specially: it clears both the -x and -v options.

       shift [number]
              The positional parameters number+1, number+2 etc. are renamed to
              1, 2, etc.  number defaults to 1.

       test expression

       [ expression ]
              test evaluates the expression and returns zero status if true, 1
              if false, and greater than 1 if there was an error.  It is  nor-
              mally  used as the condition command of if and while statements.
              The following basic expressions are available:


               str                  str has non-zero  length.   Note
                                    that  there is the potential for
                                    problems if str turns out to  be
                                    an  operator  (e.g., -r) - it is
                                    generally better to use  a  test
                                    like
                                            [ X"str" != X ]
                                    instead  (double quotes are used
                                    in case str contains  spaces  or
                                    file globing characters).
               -r file              file exists and is readable.
               -w file              file exists and is writable.
               -x file              file exists and is executable.
               -a file              file exists.
               -e file              file exists.
               -f file              file is a regular file.
               -d file              file is a directory.
               -c file              file   is  a  character  special
                                    device.
               -b file              file is a block special  device.
               -p file              file is a named pipe.
               -u file              file's  mode has setuid bit set.
               -g file              file's mode has setgid bit  set.
               -k file              file's  mode has sticky bit set.
               -s file              file is not empty.
               -O file              file's  owner  is  the   shell's
                                    effective user-ID.
               -G file              file's   group  is  the  shell's
                                    effective group-ID.
               -h file              file is a symbolic link.
               -H file              file  is  a  context   dependent
                                    directory  (only  useful  on HP-
                                    UX).
               -L file              file is a symbolic link.
               -S file              file is a socket.
               -o option            shell option  is  set  (see  set
                                    command   above   for   list  of
                                    options).   As  a   non-standard
                                    extension,  if the option starts
                                    with a !, the test  is  negated;
                                    the  test always fails if option
                                    doesn't exist (thus
                                         [ -o foo -o -o !foo ]
                                    returns  true  if  and  only  if
                                    option foo exists).
               file -nt file        first  file is newer than second
                                    file or first  file  exists  and
                                    the second file does not.
               file -ot file        first  file is older than second
                                    file or second file  exists  and
                                    the first file does not.
               file -ef file        first  file  is the same file as
                                    second file.
               -t [fd]              file descriptor is a tty device.
                                    If  the  posix  option  (set  -o
                                    posix, see POSIX Mode above)  is
                                    not  set, fd may be left out, in
                                    which case it is taken to  be  1
                                    (the  behaviour  differs  due to
                                    the    special    POSIX    rules
                                    described below).
               string               string is not empty.
               -z string            string is empty.
               -n string            string is not empty.
               string = string      strings are equal.
               string == string     strings are equal.
               string != string     strings are not equal.
               number -eq number    numbers compare equal.
               number -ne number    numbers compare not equal.

               number -ge number    numbers  compare greater than or
                                    equal.
               number -gt number    numbers compare greater than.
               number -le number    numbers  compare  less  than  or
                                    equal.
               number -lt number    numbers compare less than.

              The  above  basic  expressions,  in  which  unary operators have
              precedence over binary operators, may be combined with the  fol-
              lowing operators (listed in increasing order of precedence):


               expr -o expr    logical or
               expr -a expr    logical and
               ! expr          logical not
               ( expr )        grouping

              On  operating  systems not supporting /dev/fd/n devices (where n
              is a file descriptor number), the test command will  attempt  to
              fake  it  for  all  tests  that  operate on files (except the -e
              test).  I.e., [ -w /dev/fd/2 ] tests if  file  descriptor  2  is
              writable.

              Note  that some special rules are applied (courtesy of POSIX) if
              the number of arguments to test or [ ... ] is less than five: if
              leading  ! arguments can be stripped such that only one argument
              remains then a string length test is performed (again,  even  if
              the argument is a unary operator); if leading ! arguments can be
              stripped such that three arguments remain and the  second  argu-
              ment  is  a  binary  operator, then the binary operation is per-
              formed (even if first argument is a unary operator, including an
              unstripped !).

              Note:  A  common mistake is to use if [ $foo = bar ] which fails
              if parameter foo is null or unset, if  it  has  embedded  spaces
              (i.e.,  IFS  characters), or if it is a unary operator like ! or
              -n.  Use tests like if [ "X$foo" = Xbar ] instead.

       time [-p] [ pipeline ]
              If a pipeline is given, the times used to execute  the  pipeline
              are reported.  If no pipeline is given, then the user and system
              time used by the shell itself, and all the commands it  has  run
              since  it was started, are reported.  The times reported are the
              real time (elapsed time from start to finish), the user CPU time
              (time  spent running in user mode) and the system CPU time (time
              spent running in kernel mode).  Times are reported  to  standard
              error; the format of the output is:
                  0.00s real     0.00s user     0.00s system
              unless  the  -p  option is given (only possible if pipeline is a
              simple command), in which case the output is slightly longer:
                  real   0.00
                  user   0.00
                  sys    0.00
              (the number of digits after the decimal may vary from system  to
              system).  Note that simple redirections of standard error do not
              effect the output of the time command:
                                   time sleep 1 2> afile
                                 { time sleep 1; } 2> afile
              times for the first command do not go to afile, but those of the
              second command do.

       times  Print  the  accumulated  user and system times used by the shell
              and by processes which have exited that the shell started.

       trap [handler signal ...]
              Sets trap handler that is to be executed when any of the  speci-
              fied  signals  are  received.   Handler is either a null string,
              indicating the signals are to be ignored, a minus (-),  indicat-
              ing  that the default action is to be taken for the signals (see
              signal(3)), or a string containing shell commands to  be  evalu-
              ated  and executed at the first opportunity (i.e., when the cur-
              rent command completes, or before printing the next PS1  prompt)
              after  receipt  of  one of the signals.  Signal is the name of a
              signal (e.g., PIPE or ALRM) or the number  of  the  signal  (see
              kill  -l  command  above).   There are two special signals: EXIT
              (also known as 0), which is executed when the shell is about  to
              exit,  and ERR which is executed after an error occurs (an error
              is something that would cause the shell to exit  if  the  -e  or
              errexit  option  were  set -- see set command above).  EXIT han-
              dlers are executed in the environment of the last executed  com-
              mand.   Note  that  for non-interactive shells, the trap handler
              cannot be changed for signals that were ignored when  the  shell
              started.

              With no arguments, trap lists, as a series of trap commands, the
              current state of the traps that have been set  since  the  shell
              started.  Note that the output of trap can not be usefully piped
              to another process (an artifact  of  the  fact  that  traps  are
              cleared when subprocesses are created).

              The original Korn shell's DEBUG trap and the handling of ERR and
              EXIT traps in functions are not yet implemented.

       true   A command that exits with a zero value.

       typeset [[+-Ulprtux] [-L[n]]  [-R[n]]  [-Z[n]]  [-i[n]]  |  -f  [-tux]]
       [name[=value] ...]
              Display or set parameter attributes.  With  no  name  arguments,
              parameter  attributes are displayed: if no options arg used, the
              current attributes of all parameters are printed as typeset com-
              mands;  if  an  option is given (or - with no option letter) all
              parameters and their values with the  specified  attributes  are
              printed;  if options are introduced with +, parameter values are
              not printed.

              If name arguments are given, the attributes of the named parame-
              ters  are  set  (-)  or  cleared (+).  Values for parameters may
              optionally be specified.  If typeset is used inside a  function,
              any newly created parameters are local to the function.

              When  -f  is  used,  typeset operates on the attributes of func-
              tions.  As with parameters, if no names are given, functions are
              listed  with their values (i.e., definitions) unless options are
              introduced with +, in which case only  the  function  names  are
              reported.


               -Ln               Left justify attribute: n specifies the field
                                 width.  If n is not  specified,  the  current
                                 width  of  a  parameter  (or the width of its
                                 first assigned value) is used.  Leading white
                                 space (and zeros, if used with the -Z option)
                                 is stripped.  If necessary, values are either
                                 truncated  or  space  padded to fit the field
                                 width.
               -Rn               Right  justify  attribute:  n  specifies  the
                                 field width.  If n is not specified, the cur-
                                 rent width of a parameter (or  the  width  of
                                 its  first assigned value) is used.  Trailing
                                 white space are stripped.  If necessary, val-
                                 ues are either stripped of leading characters
                                 or space padded to make them  fit  the  field
                                 width.
               -Zn               Zero fill attribute: if not combined with -L,
                                 this is the same as -R, except  zero  padding
                                 is used instead of space padding.




               -in               integer  attribute:  n  specifies the base to
                                 use when displaying the integer (if not spec-
                                 ified, the base given in the first assignment
                                 is used).  Parameters with this attribute may
                                 be   assigned  values  containing  arithmetic
                                 expressions.
               -U                unsigned  integer  attribute:  integers   are
                                 printed  as unsigned values (only useful when
                                 combined with the -i option).  This option is
                                 not in the original Korn shell.
               -f                Function  mode:  display or set functions and
                                 their attributes, instead of parameters.
               -l                Lower case attribute: all  upper case charac-
                                 ters  in  values are converted to lower case.
                                 (In the original Korn shell,  this  parameter
                                 meant  `long  integer'  when used with the -i
                                 option).
               -p                Print complete typeset commands that  can  be
                                 used to re-create the attributes (but not the
                                 values) of parameters.  This is  the  default
                                 action  (option  exists for ksh93 compatibil-
                                 ity).
               -r                Readonly attribute: parameters with the  this
                                 attribute  may  not  be assigned to or unset.
                                 Once this attribute is set,  it  can  not  be
                                 turned off.
               -t                Tag  attribute:  has no meaning to the shell;
                                 provided for application use.

                                 For functions, -t  is  the  trace  attribute.
                                 When  functions  with the trace attribute are
                                 executed, the xtrace  (-x)  shell  option  is
                                 temporarily turned on.
               -u                Upper  case attribute: all lower case charac-
                                 ters in values are converted to  upper  case.
                                 (In  the  original Korn shell, this parameter
                                 meant `unsigned integer' when used  with  the
                                 -i  option,  which  meant  upper case letters
                                 would never be used for  bases  greater  than
                                 10.  See the -U option).

                                 For functions, -u is the undefined attribute.
                                 See Functions above for the  implications  of
                                 this.
               -x                Export  attribute:  parameters (or functions)
                                 are placed in the environment of any executed
                                 commands.   Exported functions are not imple-
                                 mented yet.

       ulimit [-abcdfHlmnpsStvw] [value]
              Display or set process limits.  If no options are used, the file
              size  limit (-f) is assumed.  value, if specified, may be either
              be an arithmetic expression or the word unlimited.   The  limits
              affect  the shell and any processes created by the shell after a
              limit is imposed.  Note that some systems may not  allow  limits
              to  be increased once they are set.  Also note that the types of
              limits available are system dependent - some systems  have  only
              the -f limit.

              -a     Displays  all  limits; unless -H is used, soft limits are
                     displayed.

              -H     Set the hard limit only (default is to set both hard  and
                     soft limits).

              -S     Set  the soft limit only (default is to set both hard and
                     soft limits).

              -b     Impose a size limit of n bytes  on  the  size  of  socket
                     buffers.

              -c     Impose  a  size  limit  of  n  blocks on the size of core
                     dumps.

              -d     Impose a size limit of n kbytes on the size of  the  data
                     area.

              -f     Impose  a  size limit of n blocks on files written by the
                     shell and its child processes (files of any size  may  be
                     read).

              -l     Impose  a  limit  of  n  kbytes  on  the amount of locked
                     (wired) physical memory.

              -m     Impose a limit of n kbytes on the amount of physical mem-
                     ory used.

              -n     Impose  a limit of n file descriptors that can be open at
                     once.

              -p     Impose a limit of n processes that can be run by the user
                     at any one time.

              -s     Impose  a size limit of n kbytes on the size of the stack
                     area.

              -t     Impose a time limit of n CPU seconds to be used  by  each
                     process.

              -v     Impose  a limit of n kbytes on the amount of virtual mem-
                     ory used; on some systems this is the  maximum  allowable
                     virtual address (in bytes, not kbytes).

              -w     Impose  a  limit  of n kbytes on the amount of swap space
                     used.

              As far as ulimit is concerned, a block is 512 bytes.

       umask [-S] [mask]
              Display or set the file permission creation mask, or umask  (see
              umask(2)).   If the -S option is used, the mask displayed or set
              is symbolic, otherwise it is an octal number.

              Symbolic masks are like those used by chmod(1):
                     [ugoa]{{=+-}{rwx}*}+[,...]
              in which the first group of characters is the who part, the sec-
              ond  group  is the op part, and the last group is the perm part.
              The who part specifies which part of the umask is  to  be  modi-
              fied.  The letters mean:

                     u      the user permissions

                     g      the group permissions

                     o      the other permissions (non-user, non-group)

                     a      all permissions (user, group and other)

              The  op  part  indicates how the who permissions are to be modi-
              fied:

                     =      set

                     +      added to

                     -      removed from

              The perm part specifies which permissions are to be  set,  added
              or removed:

                     r      read permission

                     w      write permission

                     x      execute permission

              When symbolic masks are used, they describe what permissions may
              be made available (as opposed to octal masks in which a set  bit
              means  the  corresponding  bit  is  to  be  cleared).   Example:
              `ug=rwx,o=' sets  the  mask  so  files  will  not  be  readable,
              writable  or  executable by `others', and is equivalent (on most
              systems) to the octal mask `07'.

       unalias [-adt] [name1 ...]
              The aliases for the given names are removed.  If the  -a  option
              is  used,  all aliases are removed.  If the -t or -d options are
              used, the indicated operations are carried  out  on  tracked  or
              directory aliases, respectively.

       unset [-fv] parameter ...
              Unset  the named parameters (-v, the default) or functions (-f).
              The exit status is  non-zero  if  any  of  the  parameters  were
              already unset, zero otherwise.

       wait [job]
              Wait  for  the  specified  job(s) to finish.  The exit status of
              wait is that of the last specified  job:  if  the  last  job  is
              killed  by  a signal, the exit status is 128 + the number of the
              signal (see kill -l exit-status above); if  the  last  specified
              job  can't  be  found  (because it never existed, or had already
              finished), the exit status of wait  is  127.   See  Job  Control
              below  for  the format of job.  Wait will return if a signal for
              which a trap has been set is received, or if a HUP, INT or  QUIT
              signal is received.

              If  no  jobs are specified, wait waits for all currently running
              jobs (if any) to finish and exits with a zero  status.   If  job
              monitoring  is enabled, the completion status of jobs is printed
              (this is not the case when jobs are explicitly specified).

       whence [-pv] [name ...]
              For each name, the type of command  is  listed  (reserved  word,
              built-in, alias, function, tracked alias or executable).  If the
              -p option is used, a path search done even if name is a reserved
              word,  alias,  etc.  Without the -v option, whence is similar to
              command -v except that whence will find reserved words and won't
              print  aliases  as alias commands; with the -v option, whence is
              the same as command -V.  Note that for  whence,  the  -p  option
              does  not  affect  the search path used, as it does for command.
              If the type of one or more of the names could not be determined,
              the exit status is non-zero.

   Job Control
       Job  control refers to the shell's ability to monitor and control jobs,
       which are processes or groups of  processes  created  for  commands  or
       pipelines.   At  a  minimum, the shell keeps track of the status of the
       background (i.e., asynchronous) jobs that currently exist; this  infor-
       mation  can  be  displayed  using  the jobs command.  If job control is
       fully enabled (using set -m or set -o monitor), as it is  for  interac-
       tive  shells,  the  processes  of a job are placed in their own process
       group, foreground jobs can be stopped by typing the  suspend  character
       from  the  terminal  (normally ^Z), jobs can be restarted in either the
       foreground or background, using the fg and bg  commands,  respectively,
       and  the  state  of the terminal is saved or restored when a foreground
       job is stopped or restarted, respectively.

       Note that only commands that create processes (e.g., asynchronous  com-
       mands,  subshell commands, and non-built-in, non-function commands) can
       be stopped; commands like read cannot be.

       When a job is created, it is assigned a  job-number.   For  interactive
       shells, this number is printed inside [..], followed by the process-ids
       of the processes in the job when an asynchronous command is run.  A job
       may  be  referred  to in bg, fg, jobs, kill and wait commands either by
       the process id of the last process in the command pipeline  (as  stored
       in the $! parameter) or by prefixing the job-number with a percent sign
       (%).  Other percent sequences can also be used to refer to jobs:


        %+                       The most recently stopped job, or,  if  there
                                 are  no stopped jobs, the oldest running job.
        %%, %                    Same as %+.
        %-                       The job that would be  the  %+  job,  if  the
                                 later did not exist.
        %n                       The job with job-number n.
        %?string                 The  job  containing  the  string  string (an
                                 error occurs if multiple jobs are matched).
        %string                  The job starting with string string (an error
                                 occurs if multiple jobs are matched).

       When a job changes state (e.g., a background job finishes or foreground
       job is stopped), the shell prints the following status information:
              [number] flag status command
       where

        number
              is the job-number of the job.

        flag  is + or - if the job is the %+ or %- job, respectively, or space
              if it is neither.

        status
              indicates the current state of the job and can be

              Running
                     the  job has neither stopped or exited (note that running
                     does not necessarily  mean  consuming  CPU  time  --  the
                     process could be blocked waiting for some event).

              Done [(number)]
                     the  job  exited.   number is the exit status of the job,
                     which is omitted if the status is zero.

              Stopped [(signal)]
                     the job was stopped by the indicated signal (if no signal
                     is given, the job was stopped by SIGTSTP).

              signal-description [(core dumped)]
                     the  job  was  killed  by  a  signal (e.g., Memory fault,
                     Hangup, etc. -- use kill -l for a list of signal descrip-
                     tions).   The (core dumped) message indicates the process
                     created a core file.

        command
              is the command that created the process.  If there are  multiple
              processes in the job, then each process will have a line showing
              its command and possibly its status, if it is different from the
              status of the previous process.

       When  an  attempt is made to exit the shell while there are jobs in the
       stopped state, the shell warns the user that there are stopped jobs and
       does  not  exit.   If  another  attempt is immediately made to exit the
       shell, the stopped jobs are sent a HUP  signal  and  the  shell  exits.
       Similarly,  if  the  nohup option is not set and there are running jobs
       when an attempt is made to exit a login shell, the shell warns the user
       and  does not exit.  If another attempt is immediately made to exit the
       shell, the running jobs are sent a HUP signal and the shell exits.

   Interactive Input Line Editing
       The shell supports three modes of reading command lines from a  tty  in
       an  interactive  session.   Which  is  used is controlled by the emacs,
       gmacs and vi set options (at most one of these can be set at once).  If
       none  of  these  options is enabled, the shell simply reads lines using
       the normal tty driver.  If the emacs or gmacs option is set, the  shell
       allows  emacs  like editing of the command; similarly, if the vi option
       is set, the shell allows vi like editing of the command.   These  modes
       are described in detail in the following sections.

       In  these editing modes, if a line is longer that the screen width (see
       COLUMNS parameter), a >, + or < character is displayed in the last col-
       umn  indicating that there are more characters after, before and after,
       or before the current position, respectively.   The  line  is  scrolled
       horizontally as necessary.

   Emacs Editing Mode
       When  the  emacs  option  is  set,  interactive  input  line editing is
       enabled.  Warning: This mode is slightly different from the emacs  mode
       in  the  original Korn shell and the 8th bit is stripped in emacs mode.
       In this mode various editing commands (typically bound to one  or  more
       control  characters) cause immediate actions without waiting for a new-
       line.  Several editing commands are bound to particular control charac-
       ters when the shell is invoked; these bindings can be changed using the
       following commands:

       bind   The current bindings are listed.

       bind string=[editing-command]
              The specified editing command is  bound  to  the  given  string,
              which  should consist of a control character (which may be writ-
              ten using caret notation ^X), optionally preceded by one of  the
              two  prefix  characters.   Future input of the string will cause
              the editing  command  to  be  immediately  invoked.   Note  that
              although  only  two  prefix  characters (usually ESC and ^X) are
              supported, some multi-character sequences can be supported.  The
              following  binds  the  arrow  keys on an ANSI terminal, or xterm
              (these are in the default  bindings).   Of  course  some  escape
              sequences won't work out quite this nicely:

              bind '^[['=prefix-2
              bind '^XA'=up-history
              bind '^XB'=down-history
              bind '^XC'=forward-char
              bind '^XD'=backward-char

       bind -l
              Lists the names of the functions to which keys may be bound.

       bind -m string=[substitute]
              The  specified  input  string  will  afterwards  be  immediately
              replaced by the given substitute string, which may contain edit-
              ing commands.

       The  following  is a list of editing commands available.  Each descrip-
       tion starts with the name of the command, a n, if the  command  can  be
       prefixed  with a count, and any keys the command is bound to by default
       (written using caret notation, e.g., ASCII ESC character is written  as
       ^[).   A  count prefix for a command is entered using the sequence ^[n,
       where n is a sequence of 1 or more digits; unless otherwise  specified,
       if  a  count  is  omitted, it defaults to 1.  Note that editing command
       names are used only with the bind command.  Furthermore,  many  editing
       commands  are  useful  only  on  terminals  with a visible cursor.  The
       default bindings were chosen to resemble corresponding EMACS key  bind-
       ings.   The  users tty characters (e.g., ERASE) are bound to reasonable
       substitutes and override the default bindings.

       abort ^G
              Useful as a response to a request for a  search-history  pattern
              in order to abort the search.

       auto-insert n
              Simply  causes  the  character to appear as literal input.  Most
              ordinary characters are bound to this.

       backward-char  n ^B
              Moves the cursor backward n characters.

       backward-word  n ^[B
              Moves the cursor backward to the beginning of a word; words con-
              sist of alphanumerics, underscore (_) and dollar ($).

       beginning-of-history ^[<
              Moves to the beginning of the history.

       beginning-of-line ^A
              Moves the cursor to the beginning of the edited input line.

       capitalize-word n ^[c, ^[C
              Uppercase  the  first character in the next n words, leaving the
              cursor past the end of the last word.  If the current line  does
              not  begin  with a comment character, one is added at the begin-
              ning of the line and the line is entered (as if return had  been
              pressed),  otherwise the existing comment characters are removed
              and the cursor is placed at the beginning of the line.

       complete ^[^[

       complete ^I
              Automatically completes as much as is unique of the command name
              or the file name containing the cursor.  If the entire remaining
              command or file name is unique a space is printed after its com-
              pletion,  unless  it  is  a  directory  name  in which case / is
              appended.  If there is no command or file name with the  current
              partial  word as its prefix, a bell character is output (usually
              causing a audio beep).

       complete-command ^X^[
              Automatically completes as much as is unique of the command name
              having  the  partial  word up to the cursor as its prefix, as in
              the complete command described above.

       complete-file ^[^X
              Automatically completes as much as is unique of  the  file  name
              having  the  partial  word up to the cursor as its prefix, as in
              the complete command described above.

       complete-list ^[=
              List the possible completions for the current word.

       delete-char-backward n ERASE, ^?, ^H
              Deletes n characters before the cursor.

       delete-char-forward n
              Deletes n characters after the cursor.

       delete-word-backward n ^[ERASE, ^[^?, ^[^H, ^[h
              Deletes n words before the cursor.

       delete-word-forward n ^[d
              Deletes characters after the cursor up to the end of n words.

       down-history n ^N
              Scrolls the history buffer forward n lines (later).  Each  input
              line  originally starts just after the last entry in the history
              buffer, so down-history is not useful until  either  search-his-
              tory or up-history has been performed.

       downcase-word n ^[L, ^[l
              Lowercases the next n words.

       end-of-history ^[>
              Moves to the end of the history.

       end-of-line ^E
              Moves the cursor to the end of the input line.

       eot ^_ Acts  as  an end-of-file; this is useful because edit-mode input
              disables normal terminal input canonicalization.

       eot-or-delete n ^D
              Acts as eot if alone on a line; otherwise acts  as  delete-char-
              forward.

       error  Error (ring the bell).

       exchange-point-and-mark ^X^X
              Places  the cursor where the mark is, and sets the mark to where
              the cursor was.

       expand-file ^[*
              Appends a * to the current word and replaces the word  with  the
              result  of  performing  file  globbing on the word.  If no files
              match the pattern, the bell is rung.

       forward-char n ^F
              Moves the cursor forward n characters.

       forward-word n ^[f
              Moves the cursor forward to the end of the nth word.

       goto-history n ^[g
              Goes to history number n.

       kill-line KILL
              Deletes the entire input line.

       kill-region ^W
              Deletes the input between the cursor and the mark.

       kill-to-eol n ^K
              Deletes the input from the cursor to the end of the line if n is
              not  specified,  otherwise deletes characters between the cursor
              and column n.

       list ^[?
              Prints a sorted, columnated list of command names or file  names
              (if  any) that can complete the partial word containing the cur-
              sor.  Directory names have / appended to them.

       list-command ^X?
              Prints a sorted, columnated list of command names (if any)  that
              can complete the partial word containing the cursor.

       list-file ^X^Y
              Prints a sorted, columnated list of file names (if any) that can
              complete the partial word  containing  the  cursor.   File  type
              indicators are appended as described under list above.

       newline ^J, ^M
              Causes the current input line to be processed by the shell.  The
              current cursor position may be anywhere on the line.

       newline-and-next ^O
              Causes the current input line to be processed by the shell,  and
              the  next  line  from history becomes the current line.  This is
              only useful after an up-history or search-history.

       no-op QUIT
              This does nothing.

       prefix-1 ^[
              Introduces a 2-character command sequence.

       prefix-2 ^X

       prefix-2 ^[[
              Introduces a 2-character command sequence.

       prev-hist-word n ^[., ^[_
              The last (nth) word of the previous command is inserted  at  the
              cursor.

       quote ^^
              The  following  character  is  taken literally rather than as an
              editing command.

       redraw ^L
              Reprints the prompt string and the current input line.

       search-character-backward n ^[^]
              Search backward in the current line for the  nth  occurrence  of
              the next character typed.

       search-character-forward n ^]
              Search forward in the current line for the nth occurrence of the
              next character typed.

       search-history ^R
              Enter incremental search mode.  The  internal  history  list  is
              searched  backwards for commands matching the input.  An initial
              ^ in the search string anchors the search.  The abort  key  will
              leave  search mode.  Other commands will be executed after leav-
              ing search mode.  Successive  search-history  commands  continue
              searching  backward  to the next previous occurrence of the pat-
              tern.  The history buffer retains only a finite number of lines;
              the oldest are discarded as necessary.

       set-mark-command ^[<space>
              Set the mark at the cursor position.

       stuff  On  systems  supporting it, pushes the bound character back onto
              the terminal input where it may receive  special  processing  by
              the terminal handler.  This is useful for the BRL ^T mini-systat
              feature, for example.

       stuff-reset
              Acts like stuff, then aborts input the same as an interrupt.

       transpose-chars ^T
              If at the end of line, or if  the  gmacs  option  is  set,  this
              exchanges  the  two previous characters; otherwise, it exchanges
              the previous and current characters and  moves  the  cursor  one
              character to the right.

       up-history n ^P
              Scrolls the history buffer backward n lines (earlier).

       upcase-word n ^[U, ^[u
              Uppercases the next n words.

       version ^V
              Display the version of ksh.  The current edit buffer is restored
              as soon as any key is pressed (the key is then processed, unless
              it is a space).

       yank ^Y
              Inserts the most recently killed text string at the current cur-
              sor position.

       yank-pop ^[y
              Immediately after a yank, replaces the inserted text string with
              the next previous killed text string.

   Vi Editing Mode
       The  vi  command  line editor in ksh has basically the same commands as
       the vi editor (see vi(1)), with the following exceptions:

         o    you start out in insert mode,

         o    there are file name and command completion commands  (=,  \,  *,
              ^X, ^E, ^F and, optionally, <tab>),

         o    the  _ command is different (in ksh it is the last argument com-
              mand, in vi it goes to the start of the current line),

         o    the / and G commands move in the opposite  direction  as  the  j
              command

         o    and  commands which don't make sense in a single line editor are
              not available (e.g., screen movement commands,  ex  :  commands,
              etc.).

       Note  that  the  ^X stands for control-X; also <esc>, <space> and <tab>
       are used for escape, space and tab, respectively (no kidding).

       Like vi, there are two modes: insert mode and command mode.  In  insert
       mode,  most characters are simply put in the buffer at the current cur-
       sor position as they are typed, however, some  characters  are  treated
       specially.  In particular, the following characters are taken from cur-
       rent tty settings (see stty(1)) and have their  usual  meaning  (normal
       values  are  in  parentheses):  kill (^U), erase (^?), werase (^W), eof
       (^D), intr (^C) and quit (^\).  In addition to the above, the following
       characters are also treated specially in insert mode:

        ^H                       erases previous character
        ^V                       literal next: the next character typed is not
                                 treated specially (can be used to insert  the
                                 characters being described here)
        ^J ^M                    end of line: the current line is read, parsed
                                 and executed by the shell
        <esc>                    puts the editor in command mode (see below)
        ^E                       command and file name enumeration (see below)
        ^F                       command and file name completion (see below).
                                 If used twice in a row, the list of  possible
                                 completions  is  displayed;  if  used a third
                                 time, the completion is undone.
        ^X                       command and file name expansion (see below)
        <tab>                    optional file  name  and  command  completion
                                 (see  ^F  above), enabled with set -o vi-tab-
                                 complete

       In command mode, each character is interpreted as a  command.   Charac-
       ters  that  don't  correspond  to commands, are illegal combinations of
       commands or are commands that can't be carried out all cause beeps.  In
       the  following  command  descriptions, a n indicates the command may be
       prefixed by a number (e.g., 10l moves right 10 characters); if no  num-
       ber  prefix  is  used, n is assumed to be 1 unless otherwise specified.
       The term `current position' refers to the position between  the  cursor
       and the character preceding the cursor.  A `word' is a sequence of let-
       ters, digits and underscore characters or  a  sequence  of  non-letter,
       non-digit,  non-underscore,  non-white-space  characters  (e.g., ab2*&^
       contains two words) and a `big-word' is a sequence  of  non-white-space
       characters.

       Special ksh vi commands
              The  following  commands  are not in, or are different from, the
              normal vi file editor:

              n_     insert a space followed by the nth big-word from the last
                     command  in the history at the current position and enter
                     insert mode; if n is not  specified,  the  last  word  is
                     inserted.

              #      insert the comment character (#) at the start of the cur-
                     rent line and return the line to the shell (equivalent to
                     I#^J).

              ng     like G, except if n is not specified, it goes to the most
                     recent remembered line.

              nv     edit line n using the vi editor; if n is  not  specified,
                     the  current line is edited.  The actual command executed
                     is `fc -e ${VISUAL:-${EDITOR:-vi}} n'.

              * and ^X
                     command or file name expansion is applied to the  current
                     big-word  (with  an  appended  *, if the word contains no
                     file globing characters) - the big-word is replaced  with
                     the  resulting  words.   If  the  current big-word is the
                     first on the line (or follows one of the following  char-
                     acters:  ;,  |, &, (, )) and does not contain a slash (/)
                     then command  expansion  is  done,  otherwise  file  name
                     expansion is done.  Command expansion will match the big-
                     word against all aliases, functions and built-in commands
                     as  well  as  any executable files found by searching the
                     directories in the PATH parameter.  File  name  expansion
                     matches  the  big-word  against  the files in the current
                     directory.  After expansion, the cursor  is  placed  just
                     past the last word and the editor is in insert mode.

              n\, n^F, n<tab> and n<esc>
                     command/file  name  completion:  replace the current big-
                     word with the longest unique match  obtained  after  per-
                     forming  command/file name expansion.  <tab> is only rec-
                     ognized if the vi-tabcomplete option is set, while  <esc>
                     is  only  recognized  if the vi-esccomplete option is set
                     (see set -o).  If n is specified, the nth  possible  com-
                     pletion is selected (as reported by the command/file name
                     enumeration command).

              = and ^E
                     command/file name enumeration: list all the  commands  or
                     files that match the current big-word.

              ^V     display  the  version  of  pdksh;  it  is displayed until
                     another key is pressed (this key is ignored).

              @c     macro expansion: execute the commands found in the  alias
                     _c.

       Intra-line movement commands

              nh and n^H
                     move left n characters.

              nl and n<space>
                     move right n characters.

              0      move to column 0.

              ^      move to the first non white-space character.

              n|     move to column n.

              $      move to the last character.

              nb     move back n words.

              nB     move back n big-words.

              ne     move forward to the end the word, n times.

              nE     move forward to the end the big-word, n times.

              nw     move forward n words.

              nW     move forward n big-words.

              %      find  match:  the  editor  looks  forward for the nearest
                     parenthesis, bracket or brace and then moves the  to  the
                     matching parenthesis, bracket or brace.

              nfc    move forward to the nth occurrence of the character c.

              nFc    move backward to the nth occurrence of the character c.

              ntc    move  forward  to  just  before the nth occurrence of the
                     character c.

              nTc    move backward to just before the nth  occurrence  of  the
                     character c.

              n;     repeats the last f, F, t or T command.

              n,     repeats  the  last f, F, t or T command, but moves in the
                     opposite direction.

       Inter-line movement commands

              nj and n+ and n^N
                     move to the nth next line in the history.

              nk and n- and n^P
                     move to the nth previous line in the history.

              nG     move to line n in the history; if n is not specified, the
                     number first remembered line is used.

              ng     like G, except if n is not specified, it goes to the most
                     recent remembered line.

              n/string
                     search backward through the history for the nth line con-
                     taining string; if string starts with ^, the remainder of
                     the string must appear at the start of the  history  line
                     for it to match.

              n?string
                     same  as  /,  except it searches forward through the his-
                     tory.

              nn     search for the nth occurrence of the last search  string;
                     the  direction  of  the  search  is  the same as the last
                     search.

              nN     search for the nth occurrence of the last search  string;
                     the  direction  of the search is the opposite of the last
                     search.

       Edit commands

              na     append text n times: goes into insert mode just after the
                     current  position.  The append is only replicated if com-
                     mand mode is re-entered (i.e., <esc> is used).

              nA     same as a, except it appends at the end of the line.

              ni     insert text n times: goes into insert mode at the current
                     position.   The  insertion  is only replicated if command
                     mode is re-entered (i.e., <esc> is used).

              nI     same as i, except the insertion is done just  before  the
                     first non-blank character.

              ns     substitute  the next n characters (i.e., delete the char-
                     acters and go into insert mode).

              S      substitute whole line: all characters from the first non-
                     blank character to the end of line are deleted and insert
                     mode is entered.

              ncmove-cmd
                     change from the current position to the position  result-
                     ing  from  n move-cmds (i.e., delete the indicated region
                     and go into insert mode); if  move-cmd  is  c,  the  line
                     starting from the first non-blank character is changed.

              C      change  from  the current position to the end of the line
                     (i.e., delete to the end of the line and go  into  insert
                     mode).

              nx     delete the next n characters.

              nX     delete the previous n characters.

              D      delete to the end of the line.

              ndmove-cmd
                     delete  from the current position to the position result-
                     ing from n move-cmds; move-cmd is a movement command (see
                     above) or d, in which case the current line is deleted.

              nrc    replace the next n characters with the character c.

              nR     replace: enter insert mode but overwrite existing charac-
                     ters instead of  inserting  before  existing  characters.
                     The replacement is repeated n times.

              n~     change the case of the next n characters.

              nymove-cmd
                     yank  from the current position to the position resulting
                     from n move-cmds into the yank buffer; if move-cmd is  y,
                     the whole line is yanked.

              Y      yank from the current position to the end of the line.

              np     paste the contents of the yank buffer just after the cur-
                     rent position, n times.

              nP     same as p, except the buffer is  pasted  at  the  current
                     position.

       Miscellaneous vi commands

              ^J and ^M
                     the  current  line  is  read,  parsed and executed by the
                     shell.

              ^L and ^R
                     redraw the current line.

              n.     redo the last edit command n times.

              u      undo the last edit command.

              U      undo all changes that have been made to the current line.

              intr and quit
                     the interrupt and quit terminal characters cause the cur-
                     rent line to be deleted and a new prompt to be printed.

FILES
       ~/.kshrc
       ~/.profile
       /etc/profile
       /etc/suid_profile

BUGS
       Any bugs in  pdksh  should  be  reported  to  pdksh@cs.mun.ca.   Please
       include the version of pdksh (echo $KSH_VERSION shows it), the machine,
       operating system and compiler you are using and a description of how to
       repeat  the  bug  (a  small  shell  script that demonstrates the bug is
       best).  The following, if relevant (if you are not sure, include them),
       can also helpful: options you are using (both options.h options and set
       -o options) and a copy of your config.h (the file generated by the con-
       figure   script).    New   versions  of  pdksh  can  be  obtained  from
       ftp://ftp.cs.mun.ca/pub/pdksh/.

       BTW, the most frequently reported bug is
               echo hi | read a; echo $a   # Does not print hi
       I'm aware of this and there is no need to report it.

VERSION
       This page documents version
                            @(#)PD KSH v5.2.14 99/07/13.2
       of the public domain korn shell.

AUTHORS
       This shell is based on the public domain 7th edition Bourne shell clone
       by  Charles  Forsyth  and  parts of the BRL shell by Doug A. Gwyn, Doug
       Kingston, Ron Natalie, Arnold Robbins, Lou  Salkind  and  others.   The
       first  release  of  pdksh  was created by Eric Gisin, and it was subse-
       quently maintained by John R.  MacMillan  (chance!john@sq.sq.com),  and
       Simon  J.  Gerraty  (sjg@zen.void.oz.au).   The  current  maintainer is
       Michael Rendell (michael@cs.mun.ca).   The  CONTRIBUTORS  file  in  the
       source  distribution  contains a more complete list of people and their
       part in the shell's development.

SEE ALSO
       awk(1), sh(1), csh(1), ed(1), getconf(1), getopt(1),  sed(1),  stty(1),
       vi(1),  dup(2),  execve(2),  getgid(2),  getuid(2),  open(2),  pipe(2),
       wait(2), getopt(3), rand(3), signal(3), system(3), environ(7)

       The KornShell Command and Programming Language, Morris Bolsky and David
       Korn, 1989, ISBN 0-13-516972-0.

       UNIX Shell Programming, Stephen G. Kochan, Patrick H. Wood, Hayden.

       IEEE  Standard  for  information Technology - Portable Operating System
       Interface (POSIX) - Part 2: Shell and Utilities, IEEE Inc,  1993,  ISBN
       1-55937-255-9.



                                August 19, 1996                         KSH(1)
