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

Question

In linux c program, how to print thread id of a thread created by pthread library?
for ex: we can get pid of a process by getpid()

Answer 1

There is also another way of getting thread id. While creating threads with

int pthread_create(pthread_t * thread, const pthread_attr_t * attr, void * (*start_routine)(void *), void *arg);

function call; the first parameter pthread_t * thread is actually a thread id (that is an unsigned long int defined in bits/pthreadtypes.h). Also, the last argument void *arg is the argument that is passed to void * (*start_routine) function to be threaded.

You can create a structure to pass multiple arguments and send a pointer to a structure.

typedef struct thread_info {
    pthread_t thread;
    //...
} thread_info;
//...
tinfo = malloc(sizeof(thread_info) * NUMBER_OF_THREADS);
//...
pthread_create (&tinfo[i].thread, NULL, handler, (void*)&tinfo[i]);
//...
void *handler(void *targs) {
    thread_info *tinfo = targs;
    // here you get the thread id with tinfo->thread
}