'\" 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 tcsendbreak 3 2026-07-02 "Linux man-pages 6.19"
.SH NAME
tcsendbreak
\-
send a continuous stream of zero-valued bits
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.B #include <termios.h>
.P
.BI "int tcsendbreak(int " fd ", int " duration );
.fi
.SH DESCRIPTION
.BR tcsendbreak ()
transmits a continuous stream of zero-valued bits for a specific duration,
if the terminal is using asynchronous serial data transmission.
.P
If
.I duration
is zero,
it transmits zero-valued bits
for at least 0.25 seconds,
and not more than 0.5 seconds.
.P
If
.I duration
is not zero,
it sends zero-valued bits for some
implementation-defined length of time.
.P
If the terminal is not using asynchronous serial data transmission,
.BR tcsendbreak ()
returns without taking any action.
.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 tcsendbreak ()
T}	Thread safety	MT-Safe
.TE
.\" FIXME: The markings are different from that in the glibc manual.
.\" markings in glibc manual are more detailed:
.\"
.\"     tcsendbreak: 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 VERSIONS
The effect of a nonzero
.I duration
with
.BR tcsendbreak ()
varies.
SunOS specifies a break of
.I "duration\ *\ N"
seconds, where
.I N
is at least 0.25, and not more than 0.5.
Linux, AIX, DU, Tru64 send a break of
.I duration
milliseconds.
FreeBSD and NetBSD and HP-UX and MacOS ignore the value of
.IR duration .
Under Solaris and UnixWare,
.BR tcsendbreak ()
with nonzero
.I duration
behaves like
.BR tcdrain (3).
.\" libc4 until 4.7.5, glibc for sysv: EINVAL for duration > 0.
.\" libc4.7.6, libc5, glibc for unix: duration in ms.
.\" glibc for bsd: duration in us
.\" glibc for sunos4: ignore duration
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
POSIX.1-2001.
.SH SEE ALSO
.BR tcdrain (3),
.BR tcflush (3),
.BR tcflow (3),
.BR termios (7)