bourne shell pattern matching or regular expression

powah · 06-30-2006, 08:48 AM

Is there a way to improve the following bourne shell programming?
I wonder whether there is any pattern matching or regular expression capability or function or library for bourne shell?

#! /bin/sh
# Generated automatically by configure.

for ac_option
do
case "$ac_option" in
-version | --version | --versio | --versi | --vers | --ver | --ve | --v)
echo "./config.status generated by autoconf version 2.13"
exit 0 ;;
-help | --help | --hel | --he | --h)
echo "$ac_cs_usage"; exit 0 ;;
*) echo "$ac_cs_usage"; exit 1 ;;
esac
done

binary_y2k2 · 06-30-2006, 10:10 AM

1st you posted this in the wrong sub-forum, it would be better if you had posted it in "Linux-General" but never mind.
about your question:
why dont you use grep
eg:

Code:

if echo "$ac_option"|grep "\--v">/dev/null ; then
echo "./config.status generated by autoconf version 2.13"
exit 0
elif echo "$ac_option"|grep "\--h" >/dev/null ; then
echo "$ac_cs_usage"
exit 0
else echo "$ac_cs_usage"
exit 1
fi

taylor_venable · 06-30-2006, 10:27 AM

You can make this code a little smaller using the extended globbing features available in Bash. To enable these features you need to first set the extglob option via shopt. (Unfortunately, this is not possible under Bourne shell, so if strict Bourne compatibility is what you're aiming for then this won't cut it.) The ?() glob operator will match when it's contents (inside the parens) are found either zero or one time. Here's a very simple example:

Code:

#!/usr/bin/env bash

shopt -s extglob

case $1 in
    -?(-)v?(e?(r?(s?(i?(o?(n)))))) ) echo "version" ;;
    * ) echo "not a version" ;;
esac

Since the ?() glob operator can be nested, you can achieve the desired result, although somewhat at the cost of code readability.

As an aside, this seems to me like a fairly non-standard way of doing options. Usually you only provide two mechanisms for setting an option, short (like -v) and long (like --version). But in any case this is the best solution I can come up with to do what you want.