Example: Unix Signals
Signals notify processes of internal or external events.
- the Unix software equivalent of interrupts/exceptions
- only way to do something to a process “from the outside”
- Unix systems define a small set of signal types
Examples of signal generation:
- keyboard ctrl-c and ctrl-z signal the foreground process
- synchronous fault notifications, syscall errors
- asynchronous notifications from other processes via kill
- IPC events (SIGPIPE, SIGCHLD)
- alarm notifications