psem/psem_create.c

+/* psem_create.c
+
+   Create a POSIX named semaphore.
+
+   Usage as shown in usageError().
+
+   On Linux, named semaphores are supported with kernel 2.6 or later, and
+   a glibc that provides the NPTL threading implementation.
+*/
 #include <semaphore.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include "tlpi_hdr.h"
 
 static void
 usageError(const char *progName)
 {
     fprintf(stderr, "Usage: %s [-cx] name [octal-perms [value]]\n", progName);
     fprintf(stderr, "    -c   Create semaphore (O_CREAT)\n");
     fprintf(stderr, "    -x   Create exclusively (O_EXCL)\n");
     exit(EXIT_FAILURE);
 }
 
 int
 main(int argc, char *argv[])
 {
     int flags, opt;
     mode_t perms;
     unsigned int value;
     sem_t *sem;
 
     flags = 0;
     while ((opt = getopt(argc, argv, "cx")) != -1) {
         switch (opt) {
         case 'c':   flags |= O_CREAT;           break;
         case 'x':   flags |= O_EXCL;            break;
         default:    usageError(argv[0]);
         }
     }
 
     if (optind >= argc)
         usageError(argv[0]);
 
     /* Default permissions are rw-------; default semaphore initialization
        value is 0 */
 
     perms = (argc <= optind + 1) ? (S_IRUSR | S_IWUSR) :
                 getInt(argv[optind + 1], GN_BASE_8, "octal-perms");
     value = (argc <= optind + 2) ? 0 : getInt(argv[optind + 2], 0, "value");
 
     sem = sem_open(argv[optind], flags, perms, value);
     if (sem == SEM_FAILED)
         errExit("sem_open");
 
     exit(EXIT_SUCCESS);
 }