Advanced Bash−Scripting Guide

#+ uses the second for a step interval,
#+ and continues until it reaches the third.
do
echo −n "$a "
done # 45 50 55 60 65 70 75 80
echo; echo
Advanced Bash−Scripting Guide
getopt
exit 0
The getopt command parses command−line options preceded by a dash. This external command
corresponds to the getopts Bash builtin, but it is not nearly as versatile.
Example 12−40. Using getopt to parse command−line options
#!/bin/bash
# Try the following when invoking this script.
# sh ex33a −a
# sh ex33a −abc
# sh ex33a −a −b −c
# sh ex33a −d
# sh ex33a −dXYZ
# sh ex33a −d XYZ
# sh ex33a −abcd
# sh ex33a −abcdZ
# sh ex33a −z
# sh ex33a a
# Explain the results of each of the above.
E_OPTERR=65
if [ "$#" −eq 0 ]
then # Script needs at least one command−line argument.
echo "Usage $0 −[options a,b,c]"
exit $E_OPTERR
fi
set −− `getopt "abcd:" "$@"`
# Sets positional parameters to command−line arguments.
# What happens if you use "$*" instead of "$@"?
while [ ! −z "$1" ]
do
case "$1" in
−a) echo "Option \"a\"";;
−b) echo "Option \"b\"";;
−c) echo "Option \"c\"";;
−d) echo "Option \"d\" $2";;
*) break;;
esac
shift
done
# It is better to use the 'getopts' builtin in a script,
#+ rather than 'getopt'.
# See "ex33.sh".
Chapter 12. External Filters, Programs and Commands 206