PTHREAD_SETNAME_NP(3)     (2020-11-01)      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 (aq\0aq).  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 follow-
          ing 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 follow-
          ing error:

          ERANGE
               The buffer specified by name and len is too small to
               hold the thread name.

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          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).  allbox; lbw21 lb lb l l l.
          Interface Attribute Value T{ pthread_setname_np(),
          pthread_getname_np() T}   Thread safety  MT-Safe

     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.

     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 pro-
          gram:

              $ ./a.out
              Created a thread. Default name is: a.out
              The thread name after setting it is THREADFOO.
              haZ                           # Suspend the program
              [1]+  Stopped           ./a.out
              $ ps H -C a.out -o aqpid tid cmd commaq
                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>

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          #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);
          }

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

     COLOPHON
          This page is part of release 5.10 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/.

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