sem_getvalue(3C)sem_getvalue(3C)NAMEsem_getvalue - get the value of a posix named or unnamed semaphore
SYNOPSIS
#include <semaphore.h>
int sem_getvalue(sem_t *sem, int *value);
DESCRIPTIONsem_getvalue obtains the current value of the semaphore located at
address sem, and stores it at address value. The returned value should be
viewed as a snapshot only, useful for debugging.
If the number stored at value is positive, then the semaphore is
available. If the number stored at value is zero, then the semaphore is
not available. If the number stored at value is negative, then the
semaphore is not available and the absolute value of the number
represents the number of processes currently blocked on the semaphore.
The address sem may reside anywhere in the calling processes address
space, but the process must have read and write access to sem.
sem_getvalue will fail if the following is true:
[EINVAL] The semaphore located at address sem is not a valid posix
named or unnamed semaphore.
SEE ALSOsem_init(3C), sem_destroy(3C), sem_getvalue(3C), sem_post(3C),
sem_wait(3C), sem_trywait(3C), sem_open(3C), sem_close(3C),
sem_unlink(3C),
DIAGNOSTICS
Upon successful completion, a value of 0 is returned to the calling
process. Otherwise, a value of -1 is returned and errno is set to
indicate the error.
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