Section: POSIX Programmer's Manual (3P)
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.
--- suspend or restart the transmission or reception of data
int tcflow(int fildes, int action);
function shall suspend or restart transmission or reception of data on
the object referred to by
depending on the value of
argument is an open file descriptor associated with a terminal.
is TCOOFF, output shall be suspended.
is TCOON, suspended output shall be restarted.
is TCIOFF and
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
is associated with a pseudo-terminal, the STOP character need not be
is TCION and
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
is associated with a pseudo-terminal, the START character need not be
The default on the opening of a terminal file is that neither its input
nor its output are suspended.
Attempts to use
from a process which is a member of a background process group on a
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.
Upon successful completion, 0 shall be returned. Otherwise, -1
shall be returned and
set to indicate the error.
function shall fail if:
argument is not a valid file descriptor.
argument is not a supported value.
The process group of the writing process is orphaned, the calling thread
is not blocking SIGTTOU, and the process is not ignoring SIGTTOU.
The file associated with
is not a terminal.
The following sections are informative.
The Base Definitions volume of POSIX.1-2017,
Chapter 11, General Terminal Interface,
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
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