Slide 28 of 42

Notes:

Signal - "a mechanism by which a process may be notified of, or affected by, an event occurring in the system"

Executing system code - if system code is being executed because of, for example, a read, the signal is not delivered until the read completes or errors

Signals

• signal() & raise() are ANSI C, not POSIX.1
- Use sigaction() instead


• Signal is generated, pending, delivered
- Signal not delivered if process is executing in system code; signal is delivered upon exit of system code


• Process can:
- Ignore the signal
- Execute a signal-handling function; process resumes where it was interrupted
- Restore the default action of the signal