NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON

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

NAME         top

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

SYNOPSIS         top

       #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         top

       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         top

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

ERRORS         top

       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         top

       These functions first appeared in glibc in version 2.12.

ATTRIBUTES         top

       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         top

       These functions are nonstandard GNU extensions.

NOTES         top

       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         top

       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         top

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

COLOPHON         top

       This page is part of release 4.13 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                            2017-09-15            PTHREAD_SETNAME_NP(3)

Pages that refer to this page: prctl(2)proc(5)