How do I get LWP using Linux glibc ?

Question

I developed a process with some threads on a Linux machine (Ubuntu). I'd like to know how can i get LWP from each thread (using a glibc function), once the PID and PPID are always the same for all the threads of the process.

UID        PID  PPID   LWP  C NLWP STIME TTY          TIME CMD
root      2588  2587  2588  0   11 00:05 ?        00:00:07 ./testsrv
root      2588  2587  2589  2   11 00:05 ?        00:23:17 ./testsrv
root      2588  2587  2590  0   11 00:05 ?        00:00:00 ./testsrv
root      2588  2587  2591  0   11 00:05 ?        00:00:03 ./testsrv
root      2588  2587  2592  0   11 00:05 ?        00:00:00 ./testsrv
root      2588  2587  2593  0   11 00:05 ?        00:00:00 ./testsrv
root      2588  2587  2594  0   11 00:05 ?        00:05:05 ./testsrv
root      2588  2587  2595  0   11 00:05 ?        00:00:00 ./testsrv
root      2588  2587  2596  0   11 00:05 ?        00:00:37 ./testsrv
root      2588  2587  2597  0   11 00:05 ?        00:00:00 ./testsrv
root      2588  2587  2601  0   11 00:05 ?        00:00:00 ./testsrv

Answer 1

Use gettid() from man page:

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.