sema_init(3synch)                                  sema_init(3synch)


       NAME
             sema_init - initialize a semaphore

       SYNOPSIS
             cc [options] -Kthread file
             #include <synch.h>
             int sema_init(sema_t *sema, int sema_count, int type, void *arg);

          Parameters
             sema        pointer to semaphore to initialize

             sema_count  number of resources to be protected by the
                         semaphore

             type        USYNC_THREAD or USYNC_PROCESS

             arg         NULL (reserved for future use)

       DESCRIPTION
             sema_init initializes the semaphore sema of type type to
             protect sema_count resources.  Once initialized, the semaphore
             can be used any number of times without being re-initialized.

          sema_count Parameter
             sema_count, which must be greater than or equal to zero,
             defines the initial count of resources protected by the
             semaphore.

          sema Parameter
             sema points to the semaphore to be initialized.

          type Parameter
             type can be set to one of the following values:

             USYNC_THREAD    Initialize the semaphore for threads within
                             the current process.

             USYNC_PROCESS   Initialize the semaphore for threads across
                             processes.

          arg Parameter
             arg should be set to NULL.  It is not currently used, but is
             reserved for future use.





                           Copyright 1994 Novell, Inc.               Page 1

      sema_init(3synch)                                  sema_init(3synch)


         Static Semaphore Initialization
            A semaphore can be initialized statically if its storage is
            zero-filled.  In this case, the semaphore is of type
            USYNC_THREAD, its sema_count is 0 (that is, it is ``locked'';
            no resources are available), and sema_init need not be called.
            sema_post must be called to unlock the semaphore.

         Return Values
            sema_init returns zero for success and an error number for
            failure, as described below.

         Errors
            If any of the following conditions is detected, sema_init
            returns the corresponding value:

            EINVAL   Invalid argument specified.

      USAGE
         Warnings
            sema_init does not examine the sema argument before
            initializing it.  If sema_init is called more than once for
            the same semaphore, it will overwrite its state.  It is the
            user's responsibility to ensure that sema_init is only called
            once for each semaphore.

            Operations on semaphores initialized with sema_init are not
            recursive; a thread can block itself if it attempts to
            reacquire a semaphore that it has already acquired.

      REFERENCES
            semaphore(3synch), sema_destroy(3synch), sema_post(3synch),
            sema_trywait(3synch), sema_wait(3synch), synch(3synch)
















                          Copyright 1994 Novell, Inc.               Page 2