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 .