sem_init(3p) — Linux manual page

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.

NAME

       sem_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.

       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.

       See Section 2.9.9, Synchronization Object Copies and Alternative
       Mappings for further requirements.

       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
              semaphore.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       sem_destroy(3p), sem_post(3p), sem_timedwait(3p), sem_trywait(3p)

       The Base Definitions volume of POSIX.1‐2017, semaphore.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  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.opengroup.org/unix/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               2017                      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)

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