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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 (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  recep-
       tion  of  data  on  the  object referred to by fildes, depending on the
       value of action.  The fildes argument is an open file descriptor  asso-
       ciated 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 sys-
           tem 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  back-
       ground process group on a fildes associated with its controlling termi-
       nal, 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  call-
              ing  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 Termi-
       nal 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 Electri-
       cal  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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                           TCFLOW(3P)