Man page - sem_post(3)

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Manual

sem_post

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
STANDARDS
HISTORY
NOTES
EXAMPLES
SEE ALSO

NAME

sem_post - unlock a semaphore

LIBRARY

POSIX threads library ( libpthread , -lpthread )

SYNOPSIS

#include <semaphore.h>

int sem_post(sem_t * sem );

DESCRIPTION

sem_post () increments (unlocks) the semaphore pointed to by sem . If the semaphoreโ€™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.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes (7).

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STANDARDS

POSIX.1-2008.

HISTORY

POSIX.1-2001.

NOTES

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

EXAMPLES

See sem_wait (3) and shm_open (3).

SEE ALSO

sem_getvalue (3), sem_wait (3), sem_overview (7), signal-safety (7)