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

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 represents 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 may fail if:

       EINVAL The sem argument does not refer to a valid semaphore.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       semctl(), semget(), semop(), sem_post(), sem_timedwait(), sem_trywait()

       The Base Definitions volume of POSIX.1‐2008, <semaphore.h>

COPYRIGHT

       Portions of this text are reprinted and  reproduced  in  electronic  form  from  IEEE  Std
       1003.1,  2013  Edition,  Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013  by  the
       Institute  of  Electrical  and  Electronics  Engineers,  Inc and The Open Group.  (This is
       POSIX.1-2008 with the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/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 .