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


       #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.


       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.


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


       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).


       These functions first appeared in glibc in version 2.12.


       For  an  explanation  of  the  terms  used   in   this   section,   see

       │InterfaceAttributeValue   │
       │pthread_setname_np(), │ Thread safety │ MT-Safe │
       │pthread_getname_np()  │               │         │


       These functions are nonstandard GNU extensions.


       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.


       The program below demonstrates  the  use  of  pthread_setname_np()  and

       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
           $ cat /proc/5990/task/5991/comm

   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;

       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");


           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");



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


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