PCRE_TABLE(5)                                                    PCRE_TABLE(5)



NAME
       pcre_table - format of Postfix PCRE tables

SYNOPSIS
       postmap -q "string" pcre:/etc/postfix/filename

       postmap -q - pcre:/etc/postfix/filename <inputfile

DESCRIPTION
       The  Postfix  mail  system  uses optional tables for address rewriting,
       mail routing, or access control. These tables are usually in dbm or  db
       format.

       Alternatively,  lookup tables can be specified in Perl Compatible Regu-
       lar Expression form. In this case, each input  is  compared  against  a
       list  of  patterns.  When a match is found, the corresponding result is
       returned and the search is terminated.

       To find out what types of lookup tables your  Postfix  system  supports
       use the "postconf -m" command.

       To test lookup tables, use the "postmap -q" command as described in the
       SYNOPSIS above.

COMPATIBILITY
       With Postfix version 2.2 and earlier specify "postmap -fq" to  query  a
       table that contains case sensitive patterns. Patterns are case insensi-
       tive by default.

TABLE FORMAT
       The general form of a PCRE table is:

       /pattern/flags result
              When pattern matches the input  string,  use  the  corresponding
              result value.

       !/pattern/flags result
              When  pattern  does  not  match the input string, use the corre-
              sponding result value.

       if /pattern/flags

       endif  Match the input string  against  the  patterns  between  if  and
              endif,  if  and only if that same input string also matches pat-
              tern. The if..endif can nest.

              Note: do not prepend whitespace to patterns inside if..endif.

              This feature is available in Postfix 2.1 and later.

       if !/pattern/flags

       endif  Match the input string  against  the  patterns  between  if  and
              endif, if and only if that same input string does not match pat-
              tern. The if..endif can nest.

              Note: do not prepend whitespace to patterns inside if..endif.

              This feature is available in Postfix 2.1 and later.

       blank lines and comments
              Empty lines and whitespace-only lines are ignored, as are  lines
              whose first non-whitespace character is a `#'.

       multi-line text
              A  logical  line  starts  with  non-whitespace text. A line that
              starts with whitespace continues a logical line.

       Each pattern is a perl-like regular expression. The  expression  delim-
       iter  can  be  any character, except whitespace or characters that have
       special meaning (traditionally the forward slash is used).  The regular
       expression can contain whitespace.

       By  default, matching is case-insensitive, and newlines are not treated
       as special characters. The behavior is controlled by flags,  which  are
       toggled  by appending one or more of the following characters after the
       pattern:

       i (default: on)
              Toggles the case sensitivity flag. By default, matching is  case
              insensitive.

       m (default: off)
              Toggles the PCRE_MULTILINE flag. When this flag is on, the ^ and
              $ metacharacters match immediately after and immediately  before
              a  newline  character,  respectively, in addition to matching at
              the start and end of the subject string.

       s (default: on)
              Toggles the PCRE_DOTALL flag.  When  this  flag  is  on,  the  .
              metacharacter  matches  the newline character. With Postfix ver-
              sions prior to 2.0, The flag is off by default, which is  incon-
              venient for multi-line message header matching.

       x (default: off)
              Toggles the pcre extended flag. When this flag is on, whitespace
              characters in the pattern (other than in a character class)  are
              ignored.   To include a whitespace character as part of the pat-
              tern, escape it with backslash.

              Note: do not use #comment after patterns.

       A (default: off)
              Toggles the PCRE_ANCHORED flag.  When this flag is on, the  pat-
              tern  is  forced to be "anchored", that is, it is constrained to
              match only at the start of the string which  is  being  searched
              (the  "subject  string").  This  effect  can also be achieved by
              appropriate constructs in the pattern itself.

       E (default: off)
              Toggles the PCRE_DOLLAR_ENDONLY flag. When this flag is on, a  $
              metacharacter in the pattern matches only at the end of the sub-
              ject string. Without this flag, a dollar  also  matches  immedi-
              ately  before  the  final character if it is a newline character
              (but not before any other  newline  characters).  This  flag  is
              ignored if PCRE_MULTILINE flag is set.

       U (default: off)
              Toggles  the  ungreedy matching flag.  When this flag is on, the
              pattern matching engine inverts the "greediness" of the  quanti-
              fiers  so that they are not greedy by default, but become greedy
              if followed by "?".  This flag can also set by a  (?U)  modifier
              within the pattern.

       X (default: off)
              Toggles  the  PCRE_EXTRA  flag.  When this flag is on, any back-
              slash in a pattern that is followed by a letter that has no spe-
              cial  meaning causes an error, thus reserving these combinations
              for future expansion.

SEARCH ORDER
       Patterns are applied in the order as specified in the  table,  until  a
       pattern is found that matches the input string.

       Each  pattern  is applied to the entire input string.  Depending on the
       application, that string is an entire client hostname, an entire client
       IP  address, or an entire mail address.  Thus, no parent domain or par-
       ent network search is done, and user@domain mail addresses are not bro-
       ken  up  into  their user and domain constituent parts, nor is user+foo
       broken up into user and foo.

TEXT SUBSTITUTION
       Substitution of substrings from the matched expression into the  result
       string  is  possible using the conventional perl syntax ($1, $2, etc.);
       specify $$ to produce a $ character  as  output.   The  macros  in  the
       result  string  may  need  to be written as ${n} or $(n) if they aren't
       followed by whitespace.

       Note: since negated patterns (those preceded by !) return a result when
       the  expression  does  not  match,  substitutions are not available for
       negated patterns.

EXAMPLE SMTPD ACCESS MAP
       # Protect your outgoing majordomo exploders
       /^(?!owner-)(.*)-outgoing@(.*)/ 550 Use ${1}@${2} instead

       # Bounce friend@whatever, except when whatever is our domain (you would
       # be better just bouncing all friend@ mail - this is just an example).
       /^(friend@(?!my\.domain$).*)$/  550 Stick this in your pipe $1

       # A multi-line entry. The text is sent as one line.
       #
       /^noddy@my\.domain$/
        550 This user is a funny one. You really don't want to send mail to
        them as it only makes their head spin.

EXAMPLE HEADER FILTER MAP
       /^Subject: make money fast/     REJECT
       /^To: friend@public\.com/       REJECT

EXAMPLE BODY FILTER MAP
       # First skip over base 64 encoded text to save CPU cycles.
       # Requires PCRE version 3.
       ~^[[:alnum:]+/]{60,}$~          OK

       # Put your own body patterns here.

SEE ALSO
       postmap(1), Postfix lookup table manager
       postconf(5), configuration parameters
       regexp_table(5), format of POSIX regular expression tables

README FILES
       Use "postconf readme_directory" or "postconf html_directory" to  locate
       this information.
       DATABASE_README, Postfix lookup table overview

AUTHOR(S)
       The PCRE table lookup code was originally written by:
       Andrew McNamara
       andrewm@connect.com.au
       connect.com.au Pty. Ltd.
       Level 3, 213 Miller St
       North Sydney, NSW, Australia

       Adopted and adapted by:
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA



                                                                 PCRE_TABLE(5)
