Content-type: text/html Man page of sem_getvalue

sem_getvalue

Section: C Library Functions (3)
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NAME

sem_getvalue - Get the value of a specified semaphore (P1003.1b).  

SYNOPSIS

#include <semaphore.h>

int sem_getvalue (
sem_t *sem,
int *sval);  

PARAMETERS

sem
Pointer to a specific semaphore.
sval
References a location to be updated with the value of the semaphore indicated by the sem argument.
 

DESCRIPTION

The sem_getvalue function updates a location referenced by the sval argument with the value of semaphore sem. The updated value represents an actual semaphore value that occurred during the call, but may not be the actual value of the semaphore at the time that the value is returned to the calling process.

If the semaphore is locked, the value returned will either be zero or a negative number indicating the number of processes waiting for the semaphore at some time during the call.  

RETURN VALUES

On a successful call, a value of 0 is returned. Otherwise, a value of -1 is returned and errno is set to indicate that an error occurred.  

ERRORS

The sem_getvalue function fails under the following condition:

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

RELATED INFORMATION

Functions: sem_post(3), sem_trywait(3), sem_wait(3) delim off


 

Index

NAME
SYNOPSIS
PARAMETERS
DESCRIPTION
RETURN VALUES
ERRORS
RELATED INFORMATION

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Time: 02:41:26 GMT, October 02, 2010