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



NAME
       sem_post - unlock a semaphore

SYNOPSIS
       #include <&lt;semaphore.h>&gt;

       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 semaphore.

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.

CONFORMING TO
       POSIX.1-2001.

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

EXAMPLE
       See sem_wait(3).

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

COLOPHON
       This  page  is  part of release 3.05 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                             2008-05-29                       SEM_POST(3)