sem_trywait()

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 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

Last modified: 2013-12-23

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