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sem_getvalue(3c)

Standard C Library Functions                                  sem_getvalue(3C)



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 updates 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 value returned by sem_getvalue()  is  either
       zero or a negative number whose absolute value represents the number of
       processes waiting for the semaphore at some unspecified time during the
       call.


       The  value set in sval may be 0 or positive. If sval is 0, there may be
       other processes (or LWPs or threads) waiting for the semaphore; if sval
       is positive, no process is waiting.

RETURN VALUES
       Upon  successful  completion,  sem_getvalue()  returns 0. Otherwise, it
       returns −1 and sets errno to indicate the error.

ERRORS
       The sem_getvalue() function will fail if:

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


       ENOSYS    The sem_getvalue() function is not supported by the system.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE  VALUE _ Interface StabilityCommitted _ MT-LevelMT-Safe _ Stan‐
       dardSee standards(7).


SEE ALSO
       semctl(2),    semget(2),    semop(2),    sem_post(3C),    sem_wait(3C),
       attributes(7), standards(7)



Oracle Solaris 11.4               5 Feb 2008                  sem_getvalue(3C)
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