trusty (3) sem_post.3.gz

NAME

       sem_post - unlock a semaphore

SYNOPSIS

       #include <semaphore.h>

       int sem_post(sem_t *sem);

       Link with -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.

       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 3.54 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/.