[Previous] [Contents] [Index] [Next]

Caution: This version of this document is no longer maintained. For the latest documentation, see http://www.qnx.com/developers/docs.

sem_trywait()

Wait on a semaphore, but don't block

Synopsis:

#include <semaphore.h>

int sem_trywait( sem_t * sem );

Arguments:

sem
A pointer to the sem_t object for the semaphore that you want to wait on.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The sem_trywait() function decrements the semaphore if the semaphore's value is greater than zero; otherwise, the function simply returns.

Returns:

0
The semaphore was successfully decremented.
-1
The state of the semaphore is unchanged (errno is set).

Errors:

EAGAIN
The semaphore was already locked, so it couldn't be immediately locked by the sem_trywait() function.
EDEADLK
A deadlock condition was detected.
EINVAL
Invalid semaphore descriptor sem.
EINTR
A signal interrupted this function.

Classification:

POSIX 1003.1 SEM

Safety:
Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes

See also:

sem_destroy(), sem_init(), sem_post(), sem_wait()


[Previous] [Contents] [Index] [Next]