This document is a Mac OS X manual page. Manual pages are a command-line technology for providing documentation. You can view these manual pages locally using the man(1) command. These manual pages come from many different sources, and thus, have a variety of writing styles.

This manual page is associated with the Mac OS X developer tools. The software or headers described may not be present on your Mac OS X installation until you install the developer tools package. This package is available on your Mac OS X installation DVD, and the latest versions can be downloaded from developer.apple.com.

For more information about the manual page format, see the manual page for manpages(5).

SEM_POST(2)                 BSD System Calls Manual                SEM_POST(2)

NAME
     sem_post -- unlock a semaphore

SYNOPSIS
     #include <semaphore.h>

     int
     sem_post(sem_t *sem);

DESCRIPTION
     The semaphore referenced by sem is unlocked, the value of the semaphore is incremented, and all threads
     which are waiting on the semaphore are awakened.

     sem_post() is reentrant with respect to signals and may be called from within a signal hanlder.

     If successful, sem_post() will return 0.  Otherwise, -1 is returned and errno is set.

ERRORS
     sem_post() succeeds unless:

     [EINVAL]           sem is not a valid semaphore descriptor.

SEE ALSO
     sem_open(2), sem_trywait(2), sem_wait(2), semctl(2), semget(2), semop(2)

HISTORY
     sem_post() is specified in the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995).

Darwin                           June 8, 2000                           Darwin