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Manual Pages  — SEM_INIT

NAME

sem_init – initialize an unnamed semaphore

CONTENTS

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <semaphore.h>

int
sem_init(sem_t *sem, int pshared, unsigned int value);

DESCRIPTION

The sem_init() function initializes the unnamed semaphore pointed to by sem to have the value value.

A non-zero value for pshared specifies a shared semaphore that can be used by multiple processes, the semaphore should be located in shared memory region (see mmap(2), shm_open(2), and shmget(2)), any process having read and write access to address sem can perform semaphore operations on sem.

Following a successful call to sem_init(), sem can be used as an argument in subsequent calls to sem_wait(3), sem_trywait(3), sem_post(3), and sem_destroy(3). The sem argument is no longer valid after a successful call to sem_destroy(3).

RETURN VALUES

The sem_init function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

ERRORS

The sem_init() function will fail if:
[EINVAL]
  The value argument exceeds SEM_VALUE_MAX.
[ENOSPC]
  Memory allocation error.

SEE ALSO

sem_destroy(3), sem_getvalue(3), sem_post(3), sem_trywait(3), sem_wait(3)

STANDARDS

The sem_init() function conforms to IEEE Std 1003.1-96 ("POSIX.1").

SEM_INIT (3) January 9, 2010

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