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 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 .