GENWiki

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                           # Sus-
         pend 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] : "THREAD-
     FOO");
         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); }