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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 .