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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
SEM_POST(3) Linux Programmer's Manual SEM_POST(3)
sem_post - unlock a semaphore
#include <semaphore.h>
int sem_post(sem_t *sem);
Link with -pthread.
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.
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.
EINVAL sem is not a valid semaphore.
EOVERFLOW
The maximum allowable value for a semaphore would be exceeded.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├───────────┼───────────────┼─────────┤
│sem_post() │ Thread safety │ MT-Safe │
└───────────┴───────────────┴─────────┘
POSIX.1-2001.
sem_post() is async-signal-safe: it may be safely called within a
signal handler.
See sem_wait(3) and shm_open(3).
sem_getvalue(3), sem_wait(3), sem_overview(7), signal-safety(7)
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Linux 2020-08-13 SEM_POST(3)
Pages that refer to this page: sem_close(3) , sem_destroy(3) , sem_getvalue(3) , sem_init(3) , sem_open(3) , sem_timedwait(3) , sem_timedwait(3p) , sem_trywait(3) , sem_unlink(3) , sem_wait(3) , sem_overview(7) , signal-safety(7)
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