SEM_POST(3)                                         Linux Programmer's Manual                                        SEM_POST(3)



NAME
       sem_post - unlock a semaphore

SYNOPSIS
       #include <semaphore.h>

       int sem_post(sem_t *sem);

       Link with -lrt or -pthread.

DESCRIPTION
       sem_post()  increments  (unlocks) the semaphore pointed to by sem.  If the semaphore's value consequently becomes greater
       than zero, then another process or thread blocked in a sem_wait(3) call will be woken up and proceed to  lock  the  sema-
       phore.

RETURN VALUE
       sem_post() returns 0 on success; on error, the value of the semaphore is left unchanged, -1 is returned, and errno is set
       to indicate the error.

ERRORS
       EINVAL sem is not a valid semaphore.

       EOVERFLOW
              The maximum allowable value for a semaphore would be exceeded.

CONFORMING TO
       POSIX.1-2001.

NOTES
       sem_post() is async-signal-safe: it may be safely called within a signal handler.

EXAMPLE
       See sem_wait(3).

SEE ALSO
       sem_getvalue(3), sem_wait(3), sem_overview(7)

COLOPHON
       This page is part of release 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                                                      2009-03-30                                                SEM_POST(3)