SEM_POST
NAMESYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
CONFORMING TO
NOTES
EXAMPLE
SEE ALSO
COLOPHON
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.
ATTRIBUTES
Multithreading
(see pthreads(7))
The sem_post() function is thread-safe.
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 3.69 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man−pages/.
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