NAME
sem_post —
increment (unlock) a
semaphore
LIBRARY
library “libc”
SYNOPSIS
#include
<semaphore.h>
int
sem_post(sem_t
*sem);
DESCRIPTION
Thesem_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().
The
sem_post()
function 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
The sem_post() function will fail if:
- [
EINVAL] - The sem argument points to an invalid semaphore.
- [
EOVERFLOW] - The semaphore value would exceed
SEM_VALUE_MAX.
SEE ALSO
STANDARDS
The sem_post() function conforms to
ISO/IEC 9945-1:1996 (“POSIX.1”).