sem_open — initialize and open a named semaphore
#include <semaphore.h>
sem_t
*sem_open( |
const char * | name, |
| int | oflag); |
sem_t
*sem_open( |
const char * | name, |
| int | oflag, | |
| mode_t | mode, | |
| unsigned int | value); |
sem_open() creates a new
POSIX semaphore or opens an existing semaphore. The semaphore
is identified by name. For details of the
construction of name,
see sem_overview(7).
The oflag argument
specifies flags that control the operation of the call. If
O_CREAT is specified in
oflag, then the
semaphore is created if it does not already exist. The owner
(user ID) of the semaphore is set to the effective user ID of
the calling process. The group ownership (group ID) is set to
the effective group ID of the calling process. If both
O_CREAT and O_EXCL are specified in oflag, then an error is
returned if a semaphore with the given name already exists.
If O_CREAT is specified in
oflag, then two
additional arguments must be supplied. The mode argument specifies the
permissions to be placed on the new semaphore, as for
open(2). The permissions
settings are masked against the process umask. Both read and
write permission should be granted to each class of user that
will access the semaphore. The value argument specifies the
initial value for the new semaphore. If O_CREAT is specified, and a semaphore with
the given name
already exists, then mode and value are ignored.
On success, sem_open()
returns the address of the new semaphore; this address is
used when calling other semaphore-related functions. On
error, sem_open() returns
SEM_FAILED, with errno set to indicate the error.
The semaphore exists, but the caller does not have permission to open it.
Both O_CREAT and
O_EXCL were specified in
oflag, but a
semaphore with this name already exists.
value was
greater than SEM_VALUE_MAX.
The process already has the maximum number of files and open.
name was too
long.
The system limit on the total number of open files has been reached.
The O_CREAT flag was
not specified in oflag, and no semaphore
with this name
exists.
Insufficient memory.
This page is part of release 2.79 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
|
t Copyright (C) 2006 Michael Kerrisk <mtk.manpagesgmail.com> Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. |