NAME
sem_post —
increment (unlock) a
semaphore
SYNOPSIS
#include
<semaphore.h>
int
sem_post(sem_t
*sem);
DESCRIPTION
The
sem_post()
function increments (unlocks) the semaphore pointed to by
sem. If there are threads blocked on the semaphore
when sem_post() is called, then the highest priority
thread that has been blocked the longest on the semaphore will be allowed to
return from sem_wait(3).
sem_post()
is signal-reentrant and may be called within signal handlers.
RETURN VALUES
The sem_post() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno is set to indicate the
error.
ERRORS
sem_post() will fail if:
- [
EINVAL] - sem points to an invalid semaphore.
SEE ALSO
sem_destroy(3), sem_getvalue(3), sem_init(3), sem_open(3), sem_wait(3)
STANDARDS
sem_post() conforms to
ISO/IEC 9945-1:1996 (“POSIX.1”).