pthread_setname_np(3) — Linux manual page

pthread_setname_np(3)   Library Functions Manual   pthread_setname_np(3)

NAME

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

LIBRARY

       POSIX threads library (libpthread, -lpthread)

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], size_t size);

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; size 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 size 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).

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()                │               │         │
       └─────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

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

HISTORY

       glibc 2.12.

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.

EXAMPLES

       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 <err.h>
       #include <errno.h>
       #include <pthread.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #include <unistd.h>

       #define NAMELEN 16

       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)
               errc(EXIT_FAILURE, rc, "pthread_create");

           rc = pthread_getname_np(thread, thread_name, NAMELEN);
           if (rc != 0)
               errc(EXIT_FAILURE, 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)
               errc(EXIT_FAILURE, rc, "pthread_setname_np");

           sleep(2);

           rc = pthread_getname_np(thread, thread_name, NAMELEN);
           if (rc != 0)
               errc(EXIT_FAILURE, rc, "pthread_getname_np");
           printf("The thread name after setting it is %s.\n", thread_name);

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

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

SEE ALSO

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

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Linux man-pages 6.9.1          2024-06-15          pthread_setname_np(3)

Pages that refer to this page: PR_SET_NAME(2const), proc_pid_comm(5)

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