Wed Sep 14 11:50:37 2005

Went over signals.

signals are like interrupts.  main flow of execution is suspended when
signal handler runs, and resumes when the handler ends (unless the
handler causes the program to exit)!

demonstrated shell command 'kill', which is related to but different
than Unix API 'kill'.

From the Unix shell, type
  
  man kill

to learn about shell command;

  kill -l

to list signal names and numbers;

  man -S 2 kill    (man section 2)

to see info on the Unix kill API.

we saw 2 ways to set up signal handlers:  'signal' API (on page listed
in Links area), and using the sig_action structure (in assignment
sample code).

From the shell, typing

CTRL-C  sends  SIGINT    (terminates program if it's not trapped)
CTRL-Z  sends  SIGSTOP   (suspend)
               SIGKILL   (cannot be trapped)