sigsem(2)              (XENIX Compatiblity Package)               sigsem(2)


   NAME
         sigsem - signals a process waiting on a semaphore.

   SYNOPSIS
         cc [flag ...] file ... -lx
         sigsem(int sem_num);

   DESCRIPTION
         sigsem signals a process that is waiting on the semaphore sem_num
         that it may proceed and use the resource governed by the semaphore.
         sigsem is used in conjunction with waitsem to allow synchronization
         of processes wishing to access a resource.  One or more processes may
         waitsem on the given semaphore and will be put to sleep until the
         process which currently has access to the resource issues a sigsem
         call.  If there are any waiting processes, sigsem causes the process
         which is next in line on the semaphore's queue to be rescheduled for
         execution.  The semaphore's queue is organized in First In, First Out
         (FIFO) order.

   DIAGNOSTICS
         sigsem returns the value (int) -1 if an error occurs.  If sem_num
         does not refer to a semaphore type file, errno is set to ENOTNAM.  If
         sem_num has not been previously opened by opensem, errno is set to
         EBADF.  If the process issuing a sigsem call is not the current
         ``owner'' of the semaphore (i.e., if the process has not issued a
         waitsem call before the sigsem), errno is set to ENAVAIL.

   SEE ALSO
         creatsem(2), opensem(2), waitsem(2).
























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