How to get thread id of a pthread in linux c program?

Question

In a Linux C program, how do I print the thread id of a thread created by the pthread library? For example like how we can get pid of a process by getpid().

Answer 1

What? The person asked for Linux specific, and the equivalent of getpid(). Not BSD or Apple. The answer is gettid() and returns an integral type. You will have to call it using syscall(), like this:

#include <sys/types.h> #include <unistd.h> #include <sys/syscall.h>   ....   pid_t x = syscall(__NR_gettid); 

While this may not be portable to non-linux systems, the threadid is directly comparable and very fast to acquire. It can be printed (such as for LOGs) like a normal integer.

Answer 2

pthread_self() function will give the thread id of current thread.

pthread_t pthread_self(void); 

The pthread_self() function returns the Pthread handle of the calling thread. The pthread_self() function does NOT return the integral thread of the calling thread. You must use pthread_getthreadid_np() to return an integral identifier for the thread.

NOTE:

pthread_id_np_t   tid; tid = pthread_getthreadid_np(); 

is significantly faster than these calls, but provides the same behavior.

pthread_id_np_t   tid; pthread_t         self; self = pthread_self(); pthread_getunique_np(&self, &tid);