sigsem(2)      UNIX System V(Application Compatibility Package)       sigsem(2)


NAME
      sigsem - signal a process waiting on a semaphore

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

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 (that is, 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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