sem_getvalue

Synopsis

#include <semaphore.h>

int sem_getvalue(sem_t *restrict sem, int *restrict value);

Status

Implemented

Conformance

IEEE Std 1003.1-2024

Description

The sem_getvalue() function shall store the current value of the semaphore referenced by sem in the integer referenced by value. The value is a snapshot: it may already be stale when the call returns, because another thread may lock or unlock the semaphore in the meantime.

IEEE Std 1003.1-2024 allows an implementation to report either zero or a negative number when threads are blocked on the semaphore. This implementation always reports the value itself, which is never negative.

Both named and unnamed semaphores are accepted.

Return value

Upon successful completion, sem_getvalue() shall return 0. Otherwise it shall return -1 and set errno to indicate the error.

Errors

This function shall fail if:

• EINVAL - sem is a null pointer or does not refer to a valid semaphore,

• EBADF - the named semaphore has been closed or removed.

POSIX deviations

No POSIX deviations discovered.