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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).

       ┌──────────────────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├──────────────────────┼───────────────┼─────────┤
       │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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       information about reporting bugs, and the latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.