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.1‐2008,  Chapter  11,  General  Terminal  Interface,
       <termios.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/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 .