man-pages/man2/gettid.2.html
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<HTML><HEAD><TITLE>Man page of GETTID</TITLE>
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<H1>GETTID</H1>
Section: Linux Programmer's Manual (2)<BR>Updated: 2019-03-06<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>
gettid - get thread identification
<A NAME="lbAC">&nbsp;</A>
<H2>SYNOPSIS</H2>
<PRE>
<B>#include &lt;<A HREF="file:///usr/include/sys/types.h">sys/types.h</A>&gt;</B>
<B>pid_t gettid(void);</B>
</PRE>
<A NAME="lbAD">&nbsp;</A>
<H2>DESCRIPTION</H2>
<B>gettid</B>()
returns the caller's thread ID (TID).
In a single-threaded process, the thread ID
is equal to the process ID (PID, as returned by
<B><A HREF="/cgi-bin/man/man2html?2+getpid">getpid</A></B>(2)).
In a multithreaded process, all threads
have the same PID, but each one has a unique TID.
For further details, see the discussion of
<B>CLONE_THREAD</B>
in
<B><A HREF="/cgi-bin/man/man2html?2+clone">clone</A></B>(2).
<A NAME="lbAE">&nbsp;</A>
<H2>RETURN VALUE</H2>
On success, returns the thread ID of the calling thread.
<A NAME="lbAF">&nbsp;</A>
<H2>ERRORS</H2>
This call is always successful.
<A NAME="lbAG">&nbsp;</A>
<H2>VERSIONS</H2>
The
<B>gettid</B>()
system call first appeared on Linux in kernel 2.4.11.
Library support was added in glibc 2.30.
(Earlier glibc versions did not provide a wrapper for this system call,
necessitating the use of
<B><A HREF="/cgi-bin/man/man2html?2+syscall">syscall</A></B>(2).)
<A NAME="lbAH">&nbsp;</A>
<H2>CONFORMING TO</H2>
<B>gettid</B>()
is Linux-specific and should not be used in programs that
are intended to be portable.
<A NAME="lbAI">&nbsp;</A>
<H2>NOTES</H2>
The thread ID returned by this call is not the same thing as a
POSIX thread ID (i.e., the opaque value returned by
<B><A HREF="/cgi-bin/man/man2html?3+pthread_self">pthread_self</A></B>(3)).
<P>
In a new thread group created by a
<B><A HREF="/cgi-bin/man/man2html?2+clone">clone</A></B>(2)
call that does not specify the
<B>CLONE_THREAD</B>
flag (or, equivalently, a new process created by
<B><A HREF="/cgi-bin/man/man2html?2+fork">fork</A></B>(2)),
the new process is a thread group leader,
and its thread group ID (the value returned by
<B><A HREF="/cgi-bin/man/man2html?2+getpid">getpid</A></B>(2))
is the same as its thread ID (the value returned by
<B>gettid</B>()).
<A NAME="lbAJ">&nbsp;</A>
<H2>SEE ALSO</H2>
<B><A HREF="/cgi-bin/man/man2html?2+capget">capget</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+clone">clone</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+fcntl">fcntl</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+fork">fork</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+getpid">getpid</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+get_robust_list">get_robust_list</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+ioprio_set">ioprio_set</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+perf_event_open">perf_event_open</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+sched_setaffinity">sched_setaffinity</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+sched_setparam">sched_setparam</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+sched_setscheduler">sched_setscheduler</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+tgkill">tgkill</A></B>(2),
<B><A HREF="/cgi-bin/man/man2html?2+timer_create">timer_create</A></B>(2)
<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">ERRORS</A><DD>
<DT id="6"><A HREF="#lbAG">VERSIONS</A><DD>
<DT id="7"><A HREF="#lbAH">CONFORMING TO</A><DD>
<DT id="8"><A HREF="#lbAI">NOTES</A><DD>
<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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