TCSETATTR(3)            NetBSD Library Functions Manual           TCSETATTR(3)

NAME
     cfgetispeed, cfsetispeed, cfgetospeed, cfsetospeed, cfsetspeed,
     cfmakeraw, tcgetattr, tcsetattr -- manipulating the termios structure

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <termios.h>

     speed_t
     cfgetispeed(const struct termios *t);

     int
     cfsetispeed(struct termios *t, speed_t speed);

     speed_t
     cfgetospeed(const struct termios *t);

     int
     cfsetospeed(struct termios *t, speed_t speed);

     int
     cfsetspeed(struct termios *t, speed_t speed);

     void
     cfmakeraw(struct termios *t);

     int
     tcgetattr(int fd, struct termios *t);

     int
     tcsetattr(int fd, int action, const struct termios *t);

DESCRIPTION
     The cfmakeraw, tcgetattr and tcsetattr functions are provided for getting
     and setting the termios structure.

     The cfgetispeed, cfsetispeed, cfgetospeed, cfsetospeed and cfsetspeed
     functions are provided for getting and setting the baud rate values in
     the termios structure.  The effects of the functions on the terminal as
     described below do not become effective, nor are all errors detected,
     until the tcsetattr function is called.  Certain values for baud rates
     set in the termios structure and passed to tcsetattr have special mean-
     ings.  These are discussed in the portion of the manual page that
     describes the tcsetattr function.

GETTING AND SETTING THE BAUD RATE
     The input and output baud rates are found in the termios structure.  The
     unsigned integer speed_t is typdef'd in the include file <termios.h>.
     The value of the integer corresponds directly to the baud rate being rep-
     resented, however, the following symbolic values are defined.

     #define B0      0
     #define B50     50
     #define B75     75
     #define B110    110
     #define B134    134
     #define B150    150
     #define B200    200
     #define B300    300
     #define B600    600
     #define B1200   1200
     #define B1800   1800
     #define B2400   2400
     #define B4800   4800
     #define B9600   9600
     #define B19200  19200
     #define B38400  38400
     #ifndef _POSIX_SOURCE
     #define EXTA    19200
     #define EXTB    38400
     #endif  /*_POSIX_SOURCE */

     The cfgetispeed function returns the input baud rate in the termios
     structure referenced by tp.

     The cfsetispeed function sets the input baud rate in the termios struc-
     ture referenced by tp to speed.

     The cfgetospeed function returns the output baud rate in the termios
     structure referenced by tp.

     The cfsetospeed function sets the output baud rate in the termios struc-
     ture referenced by tp to speed.

     The cfsetspeed function sets both the input and output baud rate in the
     termios structure referenced by tp to speed.

     Upon successful completion, the functions cfsetispeed, cfsetospeed, and
     cfsetspeed return a value of 0.  Otherwise, a value of -1 is returned and
     the global variable errno is set to indicate the error.

GETTING AND SETTING THE TERMIOS STATE
     This section describes the functions that are used to control the general
     terminal interface.  Unless otherwise noted for a specific command, these
     functions are restricted from use by background processes.  Attempts to
     perform these operations shall cause the process group to be sent a SIGT-
     TOU signal.  If the calling process is blocking or ignoring SIGTTOU sig-
     nals, the process is allowed to perform the operation and the SIGTTOU
     signal is not sent.

     In all the functions, although fd is an open file descriptor, the func-
     tions affect the underlying terminal file, not just the open file
     description associated with the particular file descriptor.

     The cfmakeraw function sets the flags stored in the termios structure
     (initialized by tcgetattr) to a state disabling all input and output pro-
     cessing, giving a ``raw I/O path''.  It should be noted that there is no
     function to reverse this effect.  This is because there are a variety of
     processing options that could be re-enabled and the correct method is for
     an application to snapshot the current terminal state using the function
     tcgetattr, setting raw mode with cfmakeraw and the subsequent tcsetattr,
     and then using another tcsetattr with the saved state to revert to the
     previous terminal state.

     The tcgetattr function copies the parameters associated with the terminal
     referenced by fd to the termios structure referenced by tp.  This func-
     tion is allowed from a background process, however, the terminal
     attributes may be subsequently changed by a foreground process.

     The tcsetattr function sets the parameters associated with the terminal
     from the termios structure referenced by tp.  The action field is created
     by or'ing the following values, as specified in the include file
     <termios.h>.

     TCSANOW    The change occurs immediately.

     TCSADRAIN  The change occurs after all output written to fd has been
                transmitted to the terminal.  This value of action should be
                used when changing parameters that affect output.

     TCSAFLUSH  The change occurs after all output written to fd has been
                transmitted to the terminal.  Additionally, any input that has
                been received but not read is discarded.

     TCSASOFT   If this value is or'ed into the action value, the values of
                the c_cflag, c_ispeed, and c_ospeed fields are ignored.

     The 0 baud rate is used to terminate the connection.  If 0 is specified
     as the output speed to the function tcsetattr, modem control will no
     longer be asserted on the terminal, disconnecting the terminal.

     If zero is specified as the input speed to the function tcsetattr, the
     input baud rate will be set to the same value as that specified by the
     output baud rate.

RETURN VALUES
     If tcsetattr is unable to make any of the requested changes, it returns
     -1 and sets errno.  Otherwise, it makes all of the requested changes it
     can.  If the specified input and output baud rates differ and are a com-
     bination that is not supported, neither baud rate is changed.

     Upon successful completion, the functions tcgetattr and tcsetattr return
     a value of 0.  Otherwise, they return -1 and the global variable errno is
     set to indicate the error, as follows:

     [EBADF]            The fd argument to tcgetattr or tcsetattr was not a
                        valid file descriptor.

     [EINTR]            The tcsetattr function was interrupted by a signal.

     [EINVAL]           The action argument to the tcsetattr function was not
                        valid, or an attempt was made to change an attribute
                        represented in the termios structure to an unsupported
                        value.

     [ENOTTY]           The file associated with the fd argument to tcgetattr
                        or tcsetattr is not a terminal.

SEE ALSO
     tcsendbreak(3), termios(4)

STANDARDS
     The cfgetispeed, cfsetispeed, cfgetospeed, cfsetospeed, tcgetattr and
     tcsetattr functions are expected to be compliant with the IEEE Std
     1003.1-1988 (``POSIX.1'') specification.  The cfmakeraw and cfsetspeed
     functions, as well as the TCSASOFT option to the tcsetattr function are
     extensions to the IEEE Std 1003.1-1988 (``POSIX.1'') specification.

NetBSD 5.0_STABLE                 May 1, 2004                NetBSD 5.0_STABLE
