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SEM_INIT(3P) POSIX Programmer's Manual SEM_INIT(3P)
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.
sem_init — initialize an unnamed semaphore
#include <semaphore.h>
int sem_init(sem_t *sem, int pshared, unsigned value);
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
performing 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.
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.
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.
None.
None.
None.
None.
sem_destroy(3p), sem_post(3p), sem_timedwait(3p), sem_trywait(3p)
The Base Definitions volume of POSIX.1‐2008, semaphore.h(0p)
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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 SEM_INIT(3P)
Pages that refer to this page: semaphore.h(0p), sem_close(3p), semctl(3p), sem_destroy(3p), semget(3p), semop(3p), sigaction(3p)