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sem_getvalue (3)
  • >> sem_getvalue (3) ( Solaris man: Библиотечные вызовы )
  • sem_getvalue (3) ( FreeBSD man: Библиотечные вызовы )
  • sem_getvalue (3) ( Linux man: Библиотечные вызовы )
  • sem_getvalue (3) ( POSIX man: Библиотечные вызовы )
  •  

    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(5) for descriptions of the following attributes:

    ATTRIBUTE TYPEATTRIBUTE VALUE

    Interface StabilityCommitted

    MT-Level

    Standard

     

    SEE ALSO

    semctl(2), semget(2), semop(2), sem_post(3C), sem_wait(3C), attributes(5), standards(5)


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    ERRORS
    ATTRIBUTES
    SEE ALSO


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