NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON

The Linux Programming Interface

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

NAME         top

       sem_post - unlock a semaphore

SYNOPSIS         top

       #include <semaphore.h>

       int sem_post(sem_t *sem);

       Link with -lrt or -pthread.

DESCRIPTION         top

       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         top

       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         top

       EINVAL sem is not a valid semaphore.

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

CONFORMING TO         top

       POSIX.1-2001.

NOTES         top

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

EXAMPLE         top

       See sem_wait(3).

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 3.32 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)

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