Manual Reference Pages  - SEM_POST (3)

NAME

sem_post - unlock a semaphore

CONTENTS

Synopsis
Description
Return Value
Errors
Conforming To
Notes
Example
Colophon

SYNOPSIS


#include <semaphore.h> 

int sem_post(sem_t *sem);

Link with -pthread.

DESCRIPTION

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.

RETURN VALUE

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.

ERRORS

EINVAL sem is not a valid semaphore.
EOVERFLOW
  The maximum allowable value for a semaphore would be exceeded.

CONFORMING TO

POSIX.1-2001.

NOTES

sem_post() is async-signal-safe: it may be safely called within a signal handler.

EXAMPLE

See sem_wait(3).

SEE ALSO

sem_getvalue(3), sem_wait(3), sem_overview(7)

COLOPHON

This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


Linux SEM_POST (3) 2012-05-13
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