sem_post(3)

1SEM_POST(3)                Linux Programmer's Manual               SEM_POST(3)
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NAME

6       sem_post - unlock a semaphore
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SYNOPSIS

9       #include <semaphore.h>
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11       int sem_post(sem_t *sem);
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DESCRIPTION

14       sem_post()  increments  (unlocks)  the semaphore pointed to by sem.  If
15       the semaphore's value consequently  becomes  greater  than  zero,  then
16       another  process  or thread blocked in a sem_wait(3) call will be woken
17       up and proceed to lock the semaphore.
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RETURN VALUE

20       sem_post() returns 0 on success; on error, the value of  the  semaphore
21       is  left  unchanged,  -1  is returned, and errno is set to indicate the
22       error.
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ERRORS

25       EINVAL sem is not a valid semaphore.
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CONFORMING TO

28       POSIX.1-2001.
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NOTES

31       sem_post() is async-signal-safe: it may be safely called within a  sig‐
32       nal handler.
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