sigsem(2xnx) (XENIX System Compatibility)
sigsem --
(XENIX) signal a process waiting on a semaphore
Synopsis
cc [flag . . . ] flag . . . -lx
int 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.
Return values
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.
References
creatsem(2xnx),
opensem(2xnx),
waitsem(2xnx)
30 January 1998
© 1998 The Santa Cruz Operation, Inc. All rights reserved.