SEM_POST(3) Linux Programmer's Manual SEM_POST(3)NAMEsem_post - unlock a semaphore
SYNOPSIS
#include <semaphore.h>
int sem_post(sem_t *sem);
Link with -pthread.
DESCRIPTIONsem_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 VALUEsem_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.
NOTESsem_post() is async-signal-safe: it may be safely called within a sig‐
nal handler.
EXAMPLE
See sem_wait(3).
SEE ALSOsem_getvalue(3), sem_wait(3), sem_overview(7), signal-safety(7)COLOPHON
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Linux 2017-03-13 SEM_POST(3)