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 multi-
       threaded applications.  The thread name	is  a  meaningful  C  language
       string, whose length is restricted to 16 characters, including the ter-
       minating null byte ('\0').  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  specified
       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.

ATTRIBUTES
       For  an	explanation  of	 the  terms  used   in	 this	section,   see
       attributes(7).

       +----------------------+---------------+---------+
       |Interface	      | Attribute     | Value	|
       +----------------------+---------------+---------+
       |pthread_setname_np(), | Thread safety | MT-Safe |
       |pthread_getname_np()  |		      |		|
       +----------------------+---------------+---------+

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_get-
       name_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\n", 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.\n", thread_name);

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

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

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

COLOPHON
       This page is part of release 4.10 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.



Linux				  2015-07-23		 PTHREAD_SETNAME_NP(3)