gettid() returns the thread ID of the current process.
This is equal
to the process ID (as returned by
unless the process is part of a thread group (created by specifying
the CLONE_THREAD flag to the
All processes in the same thread group
have the same PID, but each one has a unique TID.
On success, returns the thread ID of the current process.
This call is always successful.
gettid() is Linux specific and should not be used in programs that
are intended to be portable.
Glibc does not provide a wrapper for this system call; call it using