TCFLOW(3P)                                          POSIX Programmer's Manual                                         TCFLOW(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
       tcflow - suspend or restart the transmission or reception of data

SYNOPSIS
       #include <termios.h>

       int tcflow(int fildes, int action);


DESCRIPTION
       The  tcflow()  function  shall  suspend or restart transmission or reception of data on the object referred to by fildes,
       depending on the value of action. The fildes argument is an open file descriptor associated with a terminal.

        * If action is TCOOFF, output shall be suspended.

        * If action is TCOON, suspended output shall be restarted.

        * If action is TCIOFF, the system shall transmit a STOP character, which is intended to cause  the  terminal  device  to
          stop transmitting data to the system.

        * If  action  is  TCION,  the system shall transmit a START character, which is intended to cause the terminal device to
          start transmitting data to the system.

       The default on the opening of a terminal file is that neither its input nor its output are suspended.

       Attempts to use tcflow() from a process which is a member of a background process group on a fildes associated  with  its
       controlling  terminal,  shall  cause the process group to be sent a SIGTTOU signal. If the calling process is blocking or
       ignoring SIGTTOU signals, the process shall be allowed to perform the operation, and no signal is sent.

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

ERRORS
       The tcflow() function shall fail if:

       EBADF  The fildes argument is not a valid file descriptor.

       EINVAL The action argument is not a supported value.

       ENOTTY The file associated with fildes is not a terminal.


       The tcflow() 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
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       tcsendbreak(), 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                                                    TCFLOW(3P)