SEM_INIT(3) BSD Library Functions Manual SEM_INIT(3)NAMEsem_init — initialize an unnamed semaphore
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, which this
implementation is not capable of.
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 The sem argument is no longer valid after a successful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.
[EPERM] Unable to initialize a shared semaphore.
SEE ALSOsem_destroy(3), sem_getvalue(3), sem_post(3), sem_trywait(3),
sem_wait(3), sem(4)STANDARDS
The sem_init() function conforms to ISO/IEC 9945-1:1996 (“POSIX.1”).
This implementation does not support shared semaphores, and reports this
fact by setting errno to EPERM. This is perhaps a stretch of the inten‐
tion of POSIX, but is compliant, with the caveat that sem_init() always
reports a permissions error when an attempt to create a shared semaphore
is made.
BSD February 15, 2000 BSD
