Program source---pthread

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

       #define handle_error_en(en, msg) \
               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

       #define handle_error(msg) \
               do { perror(msg); exit(EXIT_FAILURE); } while (0)

       struct thread_info {    /* Used as argument to thread_start() */
           pthread_t thread_id;        /* ID returned by pthread_create() */
           int       thread_num;       /* Application-defined thread # */
           char     *argv_string;      /* From command-line argument */
       };

       /* Thread start function: display address near top of our stack,
          and return upper-cased copy of argv_string */

       static void *
       thread_start(void *arg)
       {
           struct thread_info *tinfo = arg;
           char *uargv, *p;

           printf("Thread %d: top of stack near %p; argv_string=%s\n",
                   tinfo->thread_num, &p, tinfo->argv_string);

           uargv = strdup(tinfo->argv_string);
           if (uargv == NULL)
               handle_error("strdup");

           for (p = uargv; *p != '\0'; p++)
               *p = toupper(*p);

           return uargv;
       }

       int
       main(int argc, char *argv[])
       {
           int s, tnum, opt, num_threads;
           struct thread_info *tinfo;
           pthread_attr_t attr;
           int stack_size;
           void *res;

           /* The "-s" option specifies a stack size for our threads */

           stack_size = -1;
           while ((opt = getopt(argc, argv, "s:")) != -1) {
               switch (opt) {
               case 's':
                   stack_size = strtoul(optarg, NULL, 0);
                   break;

               default:
                   fprintf(stderr, "Usage: %s [-s stack-size] arg...\n",
                           argv[0]);
                   exit(EXIT_FAILURE);
               }
           }

           num_threads = argc - optind;

           /* Initialize thread creation attributes */

           s = pthread_attr_init(&attr);
           if (s != 0)
               handle_error_en(s, "pthread_attr_init");

           if (stack_size > 0) {
               s = pthread_attr_setstacksize(&attr, stack_size);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_setstacksize");
           }

           /* Allocate memory for pthread_create() arguments */

           tinfo = calloc(num_threads, sizeof(struct thread_info));
           if (tinfo == NULL)
               handle_error("calloc");

           /* Create one thread for each command-line argument */

           for (tnum = 0; tnum < num_threads; tnum++) {
               tinfo[tnum].thread_num = tnum + 1;
               tinfo[tnum].argv_string = argv[optind + tnum];

               /* The pthread_create() call stores the thread ID into
                  corresponding element of tinfo[] */

               s = pthread_create(&tinfo[tnum].thread_id, &attr,
                                  &thread_start, &tinfo[tnum]);
               if (s != 0)
                   handle_error_en(s, "pthread_create");
           }

           /* Destroy the thread attributes object, since it is no
              longer needed */

           s = pthread_attr_destroy(&attr);
           if (s != 0)
               handle_error_en(s, "pthread_attr_destroy");

           /* Now join with each thread, and display its returned value */

           for (tnum = 0; tnum < num_threads; tnum++) {
               s = pthread_join(tinfo[tnum].thread_id, &res);
               if (s != 0)
                   handle_error_en(s, "pthread_join");

               printf("Joined with thread %d; returned value was %s\n",
                       tinfo[tnum].thread_num, (char *) res);
               free(res);      /* Free memory allocated by thread */
           }

           free(tinfo);
           exit(EXIT_SUCCESS);
       }