sem_getvalue

Name

sem_getvalue
- get the value of a semaphore

Library

libpthread.lib

Synopsis

#include <semaphore.h>

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

Return values

Upon successful completion, function return a value of zero. Otherwise, it shall return a value of -1 and set errno to indicate the error.

Detailed description

The sem_getvalue function sets the variable pointed to by sval to the current value of the semaphore pointed to by sem, as of the time that the call to sem_getvalue is actually run.

Examples

sem_t psem;   
int val;
if (sem_init(&psem, 0, 1) < 0) {
        perror("sem_init");
        return -1;
   }
if( sem_getvalue(psem, &val) == -1 ) {
  perror("sem_getvalue failed");
  return -1;
 }

Errors

The sem_getvalue function will fail if:

[`EINVAL`]
	The sem argument points to an invalid semaphore.

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