SEMOPEN(2) BSD System Calls Manual SEMOPEN(2)

NAME
     sseemmooppeenn - initialize and open a named semaphore

SYNOPSIS
     ##iinncclluuddee <>

     semt *
     sseemmooppeenn(const char *name, int oflag, ...);

     The parameters "modet mode" and "unsigned int value" are optional.

DESCRIPTION
     The named semaphore named name is initialized and opened as specified by
     the argument oflag and a semaphore descriptor is returned to the calling
     process.

     The value of oflag is formed by or'ing the following values:

           OCREAT         create the semaphore if it does not exist
           OEXCL          error if create and semaphore exists

     If OCREAT is specified, sseemmooppeenn() requires an additional two arguments.
     mode specifies the permissions for the semaphore as described in chmod(2)
     and modified by the process' umask value (see umask(2)).  The semaphore
     is created with an initial value, which must be less than or equal to
     SEMVALUEMAX.

     If OEXCL is specified and the semaphore exists, sseemmooppeenn() fails.  The
     check for the existence of the semaphore and the creation of the sema-
     phore are atomic with respect to all processes calling sseemmooppeenn() with
     OCREAT and OEXCL set.

     When a new semaphore is created, it is given the user ID and group ID
     which correspond to the effective user and group IDs of the calling
     process. There is no visible entry in the file system for the created
     object in this implementation.

     The returned semaphore descriptor is available to the calling process
     until it is closed with sseemmcclloossee(), or until the caller exits or execs.

     If a process makes repeated calls to sseemmooppeenn(), with the same name argu-
     ment, the same descriptor is returned for each successful call, unless
     sseemmuunnlliinnkk() has been called on the semaphore in the interim.

     If sseemmooppeenn() fails for any reason, it will return a value of SEMFAILED
     and sets errno.  On success, it returns a semaphore descriptor.

EERRRROORRSS
     The named semaphore is opened unless:

     [EACCES]           The required permissions (for reading and/or writing)
                        are denied for the given flags; or OCREAT is speci-
                        fied, the object does not exist, and permission to
                        create the semaphore is denied.

     [EEXIST]           OCREAT and OEXCL were specified and the semaphore
                        exists.

     [EINTR]            The sseemmooppeenn() operation was interrupted by a signal.

     [EINVAL]           The sshhmmooppeenn() operation is not supported; or OCREAT
                        is specified and value exceeds SEMVALUEMAX.

     [EMFILE]           The process has already reached its limit for sema-
                        phores or file descriptors in use.

     [ENAMETOOLONG]     name exceeded SEMNAMELEN characters.

     [ENFILE]           Too many semaphores or file descriptors are open on
                        the system.

     [ENOENT]           OCREAT is not set and the named semaphore does not
                        exist.

     [ENOSPC]           OCREAT is specified, the file does not exist, and
                        there is insufficient space available to create the
                        semaphore.

SEE ALSO
     semclose(2), sempost(2), semtrywait(2), semunlink(2), semwait(2),
     semctl(2), semget(2), semop(2), umask(2)

HISTORY     sseemmooppeenn() is specified in the POSIX Realtime Extension
     (1003.1b-1993/1003.1i-1995).

Darwin                           June 8, 2000                           Darwin