#include <errno.h>

Some functions in the library set the global variable errno when an error occurs. The file, <errno.h>, provides symbolic names for various error codes.

Warning

The errno global variable is not safe to use in a threaded or multi-task system. A race condition can occur if a task is interrupted between the call which sets error and when the task examines errno. If another task changes errno during this time, the result will be incorrect for the interrupted task.