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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13       Link with -pthread.
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DESCRIPTION

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

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

27       EINVAL sem is not a valid semaphore.
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29       EOVERFLOW
30              The maximum allowable value for a semaphore would be exceeded.
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CONFORMING TO

33       POSIX.1-2001.
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NOTES

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

40       See sem_wait(3).
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COLOPHON

46       This  page  is  part of release 3.53 of the Linux man-pages project.  A
47       description of the project, and information about reporting  bugs,  can
48       be found at http://www.kernel.org/doc/man-pages/.
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52Linux                             2012-05-13                       SEM_POST(3)