sem_init3p

Usage

#include <semaphore.h>

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Overview

The sem_init() function shall initialize the unnamed semaphore referred to by sem. The value of the initialized semaphore shall be value. Following a successful call to sem_init(), the semaphore may be used in subsequent calls to sem_wait(), sem_timedwait(), sem_trywait(), sem_post(), and sem_destroy(). This semaphore shall remain usable until the semaphore is destroyed.

If the pshared argument has a non-zero value, then the semaphore is shared between processes; in this case, any process that can access the semaphore sem can use sem for performing sem_wait(), sem_timedwait(), sem_trywait(), sem_post(), and sem_destroy() operations.

If the pshared argument is zero, then the semaphore is shared between threads of the process; any thread in this process can use sem for performing sem_wait(), sem_timedwait(), sem_trywait(), sem_post(), and sem_destroy() operations.

See Section 2.9.9, Synchronization Object Copies and Alternative Mappings for further requirements.

Attempting to initialize an already initialized semaphore results in undefined behavior.

Return value

Upon successful completion, the sem_init() function shall initialize the semaphore in sem and return 0. Otherwise, it shall return -1 and set errno to indicate the error.

Errors

The sem_init() function shall fail if:

EINVAL

The value argument exceeds {SEM_VALUE_MAX}.

ENOSPC

A resource required to initialize the semaphore has been exhausted, or the limit on semaphores ({SEM_NSEMS_MAX}) has been reached.

EPERM

The process lacks appropriate privileges to initialize the semaphore.

The following sections are informative.

Examples

None.

Application usage

None.

Rationale

None.

Future directions

None.