PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult 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  and  fildes  refers  to  a  terminal device, the system shall transmit a STOP
           character, which is intended to cause the terminal device to stop transmitting data to the system. If
           fildes is associated with a pseudo-terminal, the STOP character need not be transmitted.

        *  If action is TCION and fildes refers to  a  terminal  device,  the  system  shall  transmit  a  START
           character,  which  is intended to cause the terminal device to start transmitting data to the system.
           If fildes is associated with a pseudo-terminal, the START character need not be transmitted.

       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 thread is blocking SIGTTOU signals or the process is 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.

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

       ENOTTY The file associated with fildes is not a terminal.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       tcsendbreak()

       The Base Definitions volume of POSIX.1‐2017, Chapter 11, General Terminal Interface, <termios.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                        TCFLOW(3POSIX)