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[Linux manuál]

sem_getvalue: získejte hodnotu semaforu (REÁLNÝ ČAS)

Originální popis anglicky: sem_getvalue - get the value of a semaphore ( REALTIME)

Návod, kniha: POSIX Programmer's Manual

STRUČNĚ

#include <semaphore.h>
 
 
int sem_getvalue(sem_t *restrict sem, int *restrict sval);
 

POPIS / INSTRUKCE

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.

NÁVRATOVÁ HODNOTA

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.

CHYBY / ERRORY

The sem_getvalue() function shall fail if:
EINVAL
The sem argument does not refer to a valid semaphore.
 
The following sections are informative.

PŘÍKLADY POUŽITÍ

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.

SOUVISEJÍCÍ

semctl() , semget() , semop() , sem_post() , sem_timedwait() , sem_trywait() , sem_wait() , the Base Definitions volume of IEEE Std 1003.1-2001, <semaphore.h> 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 .
2003 IEEE/The Open Group
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