sem_getvalue(3p) - phpMan

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

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
       sem_getvalue - get the value of a semaphore (REALTIME)
SYNOPSIS
       #include <semaphore.h>
       int sem_getvalue(sem_t *restrict sem, int *restrict sval);

DESCRIPTION
       The sem_getvalue() function shall update the location referenced by the
       sval  argument  to  have  the  value of the semaphore referenced by sem
       without affecting the state of the semaphore. The updated value  repre-
       sents  an actual semaphore value that occurred at some unspecified time
       during the call, but it need not be the actual value of  the  semaphore
       when it is returned to the calling process.
       If  sem is locked, then the object to which sval points shall either be
       set to zero or to a negative number whose absolute value represents the
       number  of processes waiting for the semaphore at some unspecified time
       during the call.
RETURN VALUE
       Upon successful completion, the sem_getvalue() function shall return  a
       value  of  zero. Otherwise, it shall return a value of -1 and set errno
       to indicate the error.
ERRORS
       The sem_getvalue() function shall fail if:
       EINVAL The sem argument does not refer to a valid semaphore.

       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       The sem_getvalue() function is part of the Semaphores option  and  need
       not be available on all implementations.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       semctl(),  semget(),  semop(),  sem_post(),  sem_timedwait(),  sem_try-
       wait(),    sem_wait(),    the    Base     Definitions     volume     of
       IEEE Std 1003.1-2001, <semaphore.h>
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 .

IEEE/The Open Group                  2003                     SEM_GETVALUE(3P)