semaphore.h(0P)		   POSIX Programmer's Manual	       semaphore.h(0P)

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
       semaphore.h — semaphores

SYNOPSIS
       #include <semaphore.h>

DESCRIPTION
       The <semaphore.h> header shall define the sem_t type, used in
       performing semaphore operations. The semaphore may be implemented using
       a file descriptor, in which case applications are able to open up at
       least a total of {OPEN_MAX} files and semaphores.

       The <semaphore.h> header shall define the symbolic constant SEM_FAILED
       which shall have type sem_t *.

       The following shall be declared as functions and may also be defined as
       macros. Function prototypes shall be provided.


	   int	  sem_close(sem_t *);
	   int	  sem_destroy(sem_t *);
	   int	  sem_getvalue(sem_t *restrict, int *restrict);
	   int	  sem_init(sem_t *, int, unsigned);
	   sem_t *sem_open(const char *, int, ...);
	   int	  sem_post(sem_t *);
	   int	  sem_timedwait(sem_t *restrict, const struct timespec *restrict);
	   int	  sem_trywait(sem_t *);
	   int	  sem_unlink(const char *);
	   int	  sem_wait(sem_t *);

       Inclusion of the <semaphore.h> header may make visible symbols defined
       in the <fcntl.h> and <time.h> headers.

       The following sections are informative.

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       <fcntl.h>, <sys_types.h>, <time.h>

       The System Interfaces volume of POSIX.1‐2017, sem_close(),
       sem_destroy(), sem_getvalue(), sem_init(), sem_open(), sem_post(),
       sem_timedwait(), sem_trywait(), sem_unlink()

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		       semaphore.h(0P)