PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

SEM_INIT(3P)              POSIX Programmer's Manual             SEM_INIT(3P)

PROLOG         top

       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         top

       sem_init — initialize an unnamed semaphore

SYNOPSIS         top

       #include <semaphore.h>

       int sem_init(sem_t *sem, int pshared, unsigned value);

DESCRIPTION         top

       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.

RETURN VALUE         top

       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         top

       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         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

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

       The Base Definitions volume of POSIX.1‐2008, semaphore.h(0p)

COPYRIGHT         top

       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)