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GETTID(2)                  Linux Programmer's Manual                 GETTID(2)
NAME
       gettid - get thread identification
SYNOPSIS
       #include <sys/types.h>
       pid_t gettid(void);
       Note: There is no glibc wrapper for this system call; see NOTES.
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 process.
ERRORS
       This call is always successful.
VERSIONS
       The gettid() system call first appeared on Linux in kernel 2.4.11.
CONFORMING TO
       gettid()  is Linux-specific and should not be used in programs that are
       intended to be portable.
NOTES
       Glibc does not provide a wrapper for this system call;  call  it  using
       syscall(2).
       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), getpid(2),  get_robust_list(2),
       ioprio_set(2),   perf_event_open(2),  sched_setaffinity(2),  sched_set-
       param(2), sched_setscheduler(2), tgkill(2), timer_create(2)
COLOPHON
       This page is part of release 4.15 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/.
Linux                             2017-09-15                         GETTID(2)