#!/bin/sh
#
#         File:	on-error
#     Abstract:	Demo of tools for catching program errors in Bourne shell.
#       Author:	Bill.Costa@unh.edu -- CIS Network Information Services
#         Date:	12-OCT-2000
#
#   Example of detecting and trapping various ways a program can die.
#   The variable 'final' should be set to the desired exit code for
#   this script where we mean the following values to indicate our
#   own exit status:
#
#          0 = normal successful completion
#          1 = warning (soft error)
#          2 = fatal (hard error)
#
#   This is a work in progress.  Seems to work so far but I want to 
#   add a few more tests including catching errors based on output
#   messages.  (See "UNIX Power Tools" 48.09 'If Command Doesn't
#   Return a Status, Test the Error Messages'.)

#-------------------------------+
# Job Setup			|
#-------------------------------+

     final=2;			# Default exit code -- if we don't clear this
				# assume that something went wrong.


#-------------------------------+
# Always do the following on	|
# all possible script exits.	|
#-------------------------------+

trap 'echo "$0: end of job"; 
      exit $final;		# 'final' should always be our own exit code
     ' 0;			# for things that we are ready for.


#-------------------------------+
# Establish error handlers.	|
#-------------------------------+

trap 'echo "$0: user interrupt - aborting!";
      final=2;					# User typed CTRL+C, exit now
      exit;					# as a fatal error.
     ' 2;

trap 'echo "$0: warning - continuing";
      final=1;					# Our exit code for soft errs
     ' 10;					# when SIGUSR1 is raised.

trap 'echo "$0: hard error - aborting!";
      final=2;					# Our exit code for hard errs
      exit;					# so exit *now* when
     ' 12;					# SIGUSR2 is raised.

trap 'echo "$0: expected signal";
      final=2;					# Our exit code for signals
      exit;					# we are expecting.
     ' 3 6 8 11;

#-------------------------------+
# Main Line.			|
#-------------------------------+

     echo "
    * Try an exit code of 0 for a normal exit.
    * Try any other value for a warning exit.
    * Try signal 10 for a warning exit.
    * Try signal 12 for a fatal exit.
    * Try CNTRL+C for a user interrupt.
    * Try signals 3 6 8 or 11 for an expected interrupt.
    * Try any other signal value to halt this script totally.
";
     
     ./bail-out.pl || kill -s SIGUSR1 0;	# non-zero is a 'soft' error.

     echo "$0: the end is near" 1>&2;
     exit 9;					# This code will never be used.