PTHREAD_SETNAME_NP(3)					     Linux Programmer's Manual					     PTHREAD_SETNAME_NP(3)

NAME

       pthread_setname_np, pthread_getname_np - set/get the name of a thread

SYNOPSIS

       #define _GNU_SOURCE	       /* See feature_test_macros(7) */
       #include <pthread.h>
       int pthread_setname_np(pthread_t thread, const char *name);
       int pthread_getname_np(pthread_t thread,
			      char *name, size_t len);

       Compile and link with -pthread.

DESCRIPTION

       By  default, all the threads created using pthread_create() inherit the program name.  The pthread_setname_np() function can be used to set
       a unique name for a thread, which can be useful for debugging multithreaded applications.  The thread  name  is	a  meaningful  C  language
       string,	whose length is restricted to 16 characters, including the terminating null byte ('').  The thread argument specifies the thread
       whose name is to be changed; name specifies the new name.

       The pthread_getname_np() function can be used to retrieve the name of the thread.  The thread argument specifies the thread whose  name	is
       to be retrieved.  The buffer name is used to return the thread name; len specifies the number of bytes available in name.  The buffer spec-
       ified by name should be at least 16 characters in length.  The returned thread name in the output buffer will be null terminated.

RETURN VALUE

       On success, these functions return 0; on error, they return a nonzero error number.

ERRORS

       The pthread_setname_np() function can fail with the following error:

       ERANGE The length of the string specified pointed to by name exceeds the allowed limit.

       The pthread_getname_np() function can fail with the following error:

       ERANGE The buffer specified by name and len is too small to hold the thread name.

       If either of these functions fails to open /proc/self/task/[tid]/comm, then the call may fail with one of the errors described in open(2).

VERSIONS

       These functions first appeared in glibc in version 2.12.

CONFORMING TO

       These functions are nonstandard GNU extensions.

NOTES

       pthread_setname_np()  internally  writes  to  the  thread-specific  comm  file  under  the  /proc  filesystem:  /proc/self/task/[tid]/comm.
       pthread_getname_np() retrieves it from the same location.

EXAMPLE

       The program below demonstrates the use of pthread_setname_np() and pthread_getname_np().

       The following shell session shows a sample run of the program:

	   $ ./a.out
	   Created a thread. Default name is: a.out
	   The thread name after setting it is THREADFOO.
	   ^Z				# Suspend the program
	   [1]+  Stopped	   ./a.out
	   $ ps H -C a.out -o 'pid tid cmd comm'
	     PID   TID CMD			   COMMAND
	    5990  5990 ./a.out			   a.out
	    5990  5991 ./a.out			   THREADFOO
	   $ cat /proc/5990/task/5990/comm
	   a.out
	   $ cat /proc/5990/task/5991/comm
	   THREADFOO

   Program source

       #define _GNU_SOURCE
       #include <pthread.h>
       #include <stdio.h>
       #include <string.h>
       #include <unistd.h>
       #include <errno.h>
       #include <stdlib.h>

       #define NAMELEN 16

       #define errExitEN(en, msg) 
		   do { errno = en; perror(msg); exit(EXIT_FAILURE); 
	       } while (0)

       static void *
       threadfunc(void *parm)
       {
	   sleep(5);	      // allow main program to set the thread name
	   return NULL;
       }

       int
       main(int argc, char **argv)
       {
	   pthread_t thread;
	   int rc;
	   char thread_name[NAMELEN];

	   rc = pthread_create(&thread, NULL, threadfunc, NULL);
	   if (rc != 0)
	       errExitEN(rc, "pthread_create");

	   rc = pthread_getname_np(thread, thread_name, NAMELEN);
	   if (rc != 0)
	       errExitEN(rc, "pthread_getname_np");

	   printf("Created a thread. Default name is: %s
", thread_name);
	   rc = pthread_setname_np(thread, (argc > 1) ? argv[1] : "THREADFOO");
	   if (rc != 0)
	       errExitEN(rc, "pthread_setname_np");

	   sleep(2);

	   rc = pthread_getname_np(thread, thread_name,
				   (argc > 2) ? atoi(argv[1]) : NAMELEN);
	   if (rc != 0)
	       errExitEN(rc, "pthread_getname_np");
	   printf("The thread name after setting it is %s.
", thread_name);

	   rc = pthread_join(thread, NULL);
	   if (rc != 0)
	       errExitEN(rc, "pthread_join");

	   printf("Done
");
	   exit(EXIT_SUCCESS);
       }

SEE ALSO

       prctl(2), pthread_create(3), pthreads(7)

Linux								    2014-05-28						     PTHREAD_SETNAME_NP(3)