sem_post(3)

1SEM_POST(3)                Linux Programmer's Manual               SEM_POST(3)
2
3
4

NAME

6       sem_post - unlock a semaphore
7

SYNOPSIS

9       #include <semaphore.h>
10
11       int sem_post(sem_t *sem);
12
13       Link with -lrt or -pthread.
14

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.
20

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.
25

ERRORS

27       EINVAL sem is not a valid semaphore.
28
29       EOVERFLOW
30              The maximum allowable value for a semaphore would be exceeded.
31

CONFORMING TO

33       POSIX.1-2001.
34

NOTES

36       sem_post() is async-signal-safe: it may be safely called within a  sig‐
37       nal handler.
38

EXAMPLE

40       See sem_wait(3).
41

COLOPHON

46       This  page  is  part of release 3.25 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/.
49
50
51
52Linux                             2009-03-30                       SEM_POST(3)