man-pages/man3/sleep.3.html
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<H1>SLEEP</H1>
Section: Linux Programmer's Manual (3)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB">&nbsp;</A>
<H2>NAME</H2>
sleep - sleep for a specified number of seconds
<A NAME="lbAC">&nbsp;</A>
<H2>SYNOPSIS</H2>
<PRE>
<B>#include &lt;<A HREF="file:///usr/include/unistd.h">unistd.h</A>&gt;</B>
<B>unsigned int sleep(unsigned int </B><I>seconds</I><B>);</B>
</PRE>
<A NAME="lbAD">&nbsp;</A>
<H2>DESCRIPTION</H2>
<B>sleep</B>()
causes the calling thread to sleep either until
the number of real-time seconds specified in
<I>seconds</I>
have elapsed or until a signal arrives which is not ignored.
<A NAME="lbAE">&nbsp;</A>
<H2>RETURN VALUE</H2>
Zero if the requested time has elapsed,
or the number of seconds left to sleep,
if the call was interrupted by a signal handler.
<A NAME="lbAF">&nbsp;</A>
<H2>ATTRIBUTES</H2>
For an explanation of the terms used in this section, see
<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
<TABLE BORDER>
<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
<TR VALIGN=top><TD>
<B>sleep</B>()
</TD><TD>Thread safety</TD><TD>MT-Unsafe sig:SIGCHLD/linux<BR></TD></TR>
</TABLE>
<P>
<A NAME="lbAG">&nbsp;</A>
<H2>CONFORMING TO</H2>
POSIX.1-2001, POSIX.1-2008.
<A NAME="lbAH">&nbsp;</A>
<H2>NOTES</H2>
On Linux,
<B>sleep</B>()
is implemented via
<B><A HREF="/cgi-bin/man/man2html?2+nanosleep">nanosleep</A></B>(2).
See the
<B><A HREF="/cgi-bin/man/man2html?2+nanosleep">nanosleep</A></B>(2)
man page for a discussion of the clock used.
<A NAME="lbAI">&nbsp;</A>
<H3>Portability notes</H3>
On some systems,
<B>sleep</B>()
may be implemented using
<B><A HREF="/cgi-bin/man/man2html?2+alarm">alarm</A></B>(2)
and
<B>SIGALRM</B>
(POSIX.1 permits this);
mixing calls to
<B><A HREF="/cgi-bin/man/man2html?2+alarm">alarm</A></B>(2)
and
<B>sleep</B>()
is a bad idea.
<P>
Using
<B><A HREF="/cgi-bin/man/man2html?3+longjmp">longjmp</A></B>(3)
from a signal handler or modifying the handling of
<B>SIGALRM</B>
while sleeping will cause undefined results.
<A NAME="lbAJ">&nbsp;</A>
<H2>SEE ALSO</H2>
<B><A HREF="/cgi-bin/man/man2html?1+sleep">sleep</A></B>(1),
<B><A HREF="/cgi-bin/man/man2html?2+alarm">alarm</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+nanosleep">nanosleep</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+signal">signal</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?7+signal">signal</A></B>(7)
<A NAME="lbAK">&nbsp;</A>
<H2>COLOPHON</H2>
This page is part of release 5.05 of the Linux
<I>man-pages</I>
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
<P>
<HR>
<A NAME="index">&nbsp;</A><H2>Index</H2>
<DL>
<DT id="1"><A HREF="#lbAB">NAME</A><DD>
<DT id="2"><A HREF="#lbAC">SYNOPSIS</A><DD>
<DT id="3"><A HREF="#lbAD">DESCRIPTION</A><DD>
<DT id="4"><A HREF="#lbAE">RETURN VALUE</A><DD>
<DT id="5"><A HREF="#lbAF">ATTRIBUTES</A><DD>
<DT id="6"><A HREF="#lbAG">CONFORMING TO</A><DD>
<DT id="7"><A HREF="#lbAH">NOTES</A><DD>
<DL>
<DT id="8"><A HREF="#lbAI">Portability notes</A><DD>
</DL>
<DT id="9"><A HREF="#lbAJ">SEE ALSO</A><DD>
<DT id="10"><A HREF="#lbAK">COLOPHON</A><DD>
</DL>
<HR>
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