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
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| sem_post() | Thread safety | MT-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).COLOPHON
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