TCSETATTR(3P)                                       POSIX Programmer's Manual                                      TCSETATTR(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       tcsetattr - set the parameters associated with the terminal

SYNOPSIS
       #include <termios.h>

       int tcsetattr(int fildes, int optional_actions,
              const struct termios *termios_p);


DESCRIPTION
       The  tcsetattr()  function  shall set the parameters associated with the terminal referred to by the open file descriptor
       fildes (an open file descriptor associated with a terminal) from the termios structure referenced by  termios_p  as  fol-
       lows:

        * If optional_actions is TCSANOW, the change shall occur immediately.

        * If optional_actions is TCSADRAIN, the change shall occur after all output written to fildes is transmitted. This func-
          tion should be used when changing parameters that affect output.

        * If optional_actions is TCSAFLUSH, the change shall occur after all output written to fildes is  transmitted,  and  all
          input so far received but not read shall be discarded before the change is made.

       If the output baud rate stored in the termios structure pointed to by termios_p is the zero baud rate, B0, the modem con-
       trol lines shall no longer be asserted. Normally, this shall disconnect the line.

       If the input baud rate stored in the termios structure pointed to by termios_p is 0, the input baud  rate  given  to  the
       hardware is the same as the output baud rate stored in the termios structure.

       The  tcsetattr()  function shall return successfully if it was able to perform any of the requested actions, even if some
       of the requested actions could not be performed. It shall set all the attributes  that  the  implementation  supports  as
       requested  and  leave all the attributes not supported by the implementation unchanged.  If no part of the request can be
       honored, it shall return -1 and set errno to [EINVAL]. If the input and output baud rates differ and  are  a  combination
       that is not supported, neither baud rate shall be changed. A subsequent call to tcgetattr() shall return the actual state
       of the terminal device (reflecting both the changes made and not made in the previous tcsetattr() call). The  tcsetattr()
       function shall not change the values found in the termios structure under any circumstances.

       The effect of tcsetattr() is undefined if the value of the termios structure pointed to by termios_p was not derived from
       the result of a call to tcgetattr() on fildes; an application should modify only fields and flags defined by this  volume
       of IEEE Std 1003.1-2001 between the call to tcgetattr() and tcsetattr(), leaving all other fields and flags unmodified.

       No  actions  defined by this volume of IEEE Std 1003.1-2001, other than a call to tcsetattr() or a close of the last file
       descriptor in the system associated with this terminal device, shall cause any of the terminal attributes defined by this
       volume of IEEE Std 1003.1-2001 to change.

       If  tcsetattr()  is called from a process which is a member of a background process group on a fildes associated with its
       controlling terminal:

        * If the calling process is blocking or ignoring SIGTTOU signals, the operation completes  normally  and  no  signal  is
          sent.

        * Otherwise, a SIGTTOU signal shall be sent to the process group.

RETURN VALUE
       Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.

ERRORS
       The tcsetattr() function shall fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       EINTR  A signal interrupted tcsetattr().

       EINVAL The  optional_actions argument is not a supported value, or an attempt was made to change an attribute represented
              in the termios structure to an unsupported value.

       ENOTTY The file associated with fildes is not a terminal.


       The tcsetattr() function may fail if:

       EIO    The process group of the writing process is orphaned, and the writing process is not ignoring or blocking SIGTTOU.


       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       If trying to change baud rates, applications should call tcsetattr() then call tcgetattr() in  order  to  determine  what
       baud rates were actually selected.

RATIONALE
       The tcsetattr() function can be interrupted in the following situations:

        * It is interrupted while waiting for output to drain.

        * It is called from a process in a background process group and SIGTTOU is caught.

       See also the RATIONALE section in tcgetattr().

FUTURE DIRECTIONS
       Using an input baud rate of 0 to set the input rate equal to the output rate may not necessarily be supported in a future
       version of this volume of IEEE Std 1003.1-2001.

SEE ALSO
       cfgetispeed(), tcgetattr(), the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 11, General Terminal  Interface,
       <termios.h>, <unistd.h>

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open  Group
       Standard   is   the   referee   document.   The   original   Standard   can   be   obtained  online  at  http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                 TCSETATTR(3P)