sem_trywait Return Values

sem_trywait() returns zero after completing successfully. Any other return value indicates that an error occurred. When any of the following conditions occurs, the function fails and returns the corresponding value.

EINVAL

Description:

sem points to an illegal address.

EINTR

Description:

A signal interrupted this function.

EAGAIN

Description:

The semaphore was already locked, so the semaphore cannot be immediately locked by the sem_trywait() operation.