CS 3733 Operating Systems

Lecture 25 [3/11/98]: Catching Signals

Reading: Sections 5.3-5.4 of PUP

Signal masks and signal sets:

Signal mask is associated with blocking of signals. These signals are not lost---their delivery is just postponed.
Signal set operations: sigemptyset, sigfillset, sigaddset, sigdelset, sigismember
Signal mask operations are performed by calling sigprocmask with SIG_BLOCK, SIG_UNBLOCK and SIG_SETMASK.

Catching signals

In order to catch a signal, you must install a handler with sigaction
SIG_DFL is the default handler.
SIG_IGN indicates the signal should be thrown away. (You should understand why this is different than blocking a signal.)
pause suspends a process until a signal is delivered.
sigsuspend does an atomic unblock and suspend for a set of signals.

System calls and signals

What does it mean to be asynch-signal safe?
Interruption of long calls.

Skill: Understand how to catch a signal

Revision Date: 3/10/98