gettid(2) — Linux manual page


GETTID(2)               Linux Programmer's Manual              GETTID(2)

NAME         top

       gettid - get thread identification

SYNOPSIS         top

       #define _GNU_SOURCE
       #include <unistd.h>

       pid_t gettid(void);

DESCRIPTION         top

       gettid() 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 getpid(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 CLONE_THREAD in clone(2).

RETURN VALUE         top

       On success, returns the thread ID of the calling thread.

ERRORS         top

       This call is always successful.

VERSIONS         top

       The gettid() 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 syscall(2).)

CONFORMING TO         top

       gettid() is Linux-specific and should not be used in programs
       that are intended to be portable.

NOTES         top

       The thread ID returned by this call is not the same thing as a
       POSIX thread ID (i.e., the opaque value returned by

       In a new thread group created by a clone(2) call that does not
       specify the CLONE_THREAD flag (or, equivalently, a new process
       created by fork(2)), the new process is a thread group leader,
       and its thread group ID (the value returned by getpid(2)) is the
       same as its thread ID (the value returned by gettid()).

SEE ALSO         top

       capget(2), clone(2), fcntl(2), fork(2), get_robust_list(2),
       getpid(2), ioprio_set(2), perf_event_open(2),
       sched_setaffinity(2), sched_setparam(2), sched_setscheduler(2),
       tgkill(2), timer_create(2)

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at

Linux                          2021-03-22                      GETTID(2)

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