sem_trywait()
QNX SDP8.0C Library ReferenceAPIDeveloper
Wait on a named or unnamed 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 count wasn't greater then 0, so sem_trywait() couldn't immediately decrement it.
- EINVAL
- Invalid semaphore descriptor sem.
- EINTR
- A signal interrupted this function.
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |
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