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NAME
       gettid - get thread identification


SYNOPSIS
       #define _GNU_SOURCE
       #include <unistd.h>
       #include <sys/types.h>

       pid_t gettid(void);


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


ERRORS
       This call is always successful.


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


NOTES
       The  thread ID returned by this call is not the same thing as a POSIX thread ID (i.e., the
       opaque value returned by pthread_self(3)).

       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
       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
       This  page  is  part of release 5.10 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 https://www.kernel.org/doc/man-pages/.