GETTID(2)

NAME
gettid - get thread identification

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS
#define _GNU_SOURCE
#include <unistd.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).)

STANDARDS
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)