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  ('\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; hence the suffix  "_np"  (nonportable)  in
       the names.

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\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

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