pthread_setname_np

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
       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
       This page is part of release 5.03 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                             2019-03-06             PTHREAD_SETNAME_NP(3)