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Linux 2.6 - man page for pthread_getname_np (linux section 3)

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,
			      const 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 lan-
       guage string, whose length is restricted to 16 characters, including the terminating  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.

CONFORMING TO
       These functions are nonstandard GNU extensions.

NOTES
       pthread_setname_np()  internally  writes  to  the  thread  specific  comm file under /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\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 3.55 of the Linux man-pages project.  A description of the
       project, and information about reporting bugs, can be found at
       http://www.kernel.org/doc/man-pages/.

Linux					    2013-06-21			    PTHREAD_SETNAME_NP(3)


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