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, Copyright (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.opengroup.org/unix/online.html .

IEEE/The Open Group                                   2003                                             TCFLOW(P)