NAME

       semaphore.h - semaphores (REALTIME)

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
       symbol SEM_FAILED shall be defined (see sem_open()).

       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 headers
       <fcntl.h> and <sys/types.h>.

       The following sections are informative.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       <fcntl.h>  ,  <sys/types.h>  ,  the  System  Interfaces  volume  of  IEEE Std 1003.1-2001,
       sem_destroy(),   sem_getvalue(),   sem_init(),  sem_open(),  sem_post(),  sem_timedwait(),
       sem_trywait(), sem_unlink(), sem_wait()

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1,  2003  Edition,  Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  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 .