SEM_INIT(3P) POSIX Programmer's Manual SEM_INIT(3P)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.
NAMEsem_init — initialize an unnamed semaphore
SYNOPSIS
#include <semaphore.h>
int sem_init(sem_t *sem, int pshared, unsigned value);
DESCRIPTION
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.
Only sem itself may be used for performing synchronization. The result
of referring to copies of sem in calls to sem_wait(), sem_timedwait(),
sem_trywait(), sem_post(), and sem_destroy() is undefined.
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 per‐
forming sem_wait(), sem_timedwait(), sem_trywait(), sem_post(), and
sem_destroy() operations. The use of the semaphore by threads other
than those created in the same process is undefined.
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 sema‐
phore.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOsem_destroy(), sem_post(), sem_timedwait(), sem_trywait()
The Base Definitions volume of POSIX.1‐2008, <semaphore.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 SEM_INIT(3P)
