gettid - get thread identification
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).
On success, returns the thread ID of the calling thread.
This call is always successful.
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
gettid() is Linux-specific and should not be used in programs that are
intended to be portable.
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()).
capget(2), clone(2), fcntl(2), fork(2),
getpid(2), get_robust_list(2), ioprio_set(2),
sched_setparam(2), sched_setscheduler(2), tgkill(2),
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