'\" t
.\" Copyright 2006-2015, Michael Kerrisk <mtk.manpages@gmail.com>
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.TH tcflow 3 2026-07-02 "Linux man-pages 6.19"
.SH NAME
tcflow
\-
suspect transmission or reception of data
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.B #include <termios.h>
.P
.BI "int tcflow(int " fd ", int " action );
.fi
.SH DESCRIPTION
.BR tcflow ()
suspends transmission or reception of data
on the object referred to by
.IR fd ,
depending on the value of
.IR action :
.TP
.B TCOOFF
suspends output.
.TP
.B TCOON
restarts suspended output.
.TP
.B TCIOFF
transmits a STOP character,
which stops the terminal device from
transmitting data to the system.
.TP
.B TCION
transmits a START character,
which starts the terminal device
transmitting data to the system.
.P
The default on open of a terminal file is that
neither its input nor its output is suspended.
.SH RETURN VALUE
.TP
.B 0
on success.
.TP
.B \-1
on failure and set
.I errno
to indicate the error.
.SH ATTRIBUTES
For an explanation of the terms used in this section,
see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR tcflow ()
T}	Thread safety	MT-Safe
.TE
.\" FIXME: The markings are different from that in the glibc manual.
.\" markings in glibc manual are more detailed:
.\"
.\"     tcflow: MT-Unsafe race:tcattr(filedes)/bsd
.\"
.\" glibc manual says /bsd indicate the preceding marker only applies
.\" when the underlying kernel is a BSD kernel.
.\" So, it is safety in Linux kernel.
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
POSIX.1-2001.
.SH SEE ALSO
.BR tcsendbreak (3),
.BR tcdrain (3),
.BR tcflush (3),
.BR termios (7)