Advanced Bash−Scripting Guide

next_gen "$Cur"
let "generation += 1"
done
# ==============================================================
echo
exit 0
Advanced Bash−Scripting Guide
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# The grid in this script has a "boundary problem".
# The the top, bottom, and sides border on a void of dead cells.
# Exercise: Change the script to have the grid wrap around,
# + so that the left and right sides will "touch",
# + as will the top and bottom.
Example A−12. Data file for "Game of Life"
# This is an example "generation 0" start−up file for "life.sh".
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# The "gen0" file is a 10 x 10 grid using a period (.) for live cells,
#+ and an underscore (_) for dead ones. We cannot simply use spaces
#+ for dead cells in this file because of a peculiarity in Bash arrays.
# [Exercise for the reader: explain this.]
#
# Lines beginning with a '#' are comments, and the script ignores them.
__.__..___
___._.____
____.___..
_._______.
____._____
..__...___
____._____
___...____
__.._..___
_..___..__
+++
The following two scripts are by Mark Moraes of the University of Toronto. See the enclosed file
"Moraes−COPYRIGHT" for permissions and restrictions.
Example A−13. behead: Removing mail and news message headers
#! /bin/sh
# Strips off the header from a mail/News message i.e. till the first
# empty line
# Mark Moraes, University of Toronto
# ==> These comments added by author of this document.
if [ $# −eq 0 ]; then
# ==> If no command line args present, then works on file redirected to stdin.
sed −e '1,/^$/d' −e '/^[ ]*$/d'
# −−> Delete empty lines and all lines until
# −−> first one beginning with white space.
else
Appendix A. Contributed Scripts 385