[Bash] Variable exapansion and variables within variables

Question

To make the following script more reusable, I wanted to refactor the "pattern" in a separate variable for the renameit2 function to use. However, it
currently doesn't work; "tr" throws an error:
tr: extra operand `\'-\''"
Can anyone explain how I can achieve what I'm trying to do?
Here is the complete script:
old="Hello THIS & test"
renameit() {
new=$(echo $old | \
tr ' ' '-' | tr -d '[{}(),\!]' | tr -d "\'" | tr '[A-Z]' '[a-z]' | \
sed -e 's/---/-/g' -e 's/&/-and-/g' -e 's/--/-/g' -e 's/_/-/g')
echo $new
PATTERN="
tr ' ' '-' | tr -d '[{}(),\!]' | tr -d "\'" | tr '[A-Z]' '[a-z]' | \
sed -e 's/---/-/g' -e 's/&/-and-/g' -e 's/--/-/g' -e 's/_/-/g'
renameit2() {
new=$(echo $old | $PATTERN)
echo $new
case $1 in
old)
renameit
new)
renameit2
esac

Answer 1

Hi,
I reworked your solution to use an array of sed expressions.
It becomes
patterns=( "s/[A-Z]*/\L\\\&/g" #replace uppercase with lowercase (\L\&)
"s/ /-/g" #replace spaces
"s/[{}\(\),\\!]//g" #delete some special chars
"s/\'//g" #delete the single quote
"s/[\\d038]/-and-/g" #replace the amperstad (ascii no 38 decimal)
"s/_/-/g" #replace underscores with dashes
"s/-\{2,\}/-/g" ) #translate all series of dashes to just one dash
renameit2() {
new="$old"
for p in "${patterns[@]}"
do
new=$(echo $new|sed -e "$p")
if [ -z "$new" ] ; then
echo "Failure at expression ${p}"
fi
done
echo $new
You could possibly do some xargs magic to cut the loop, but I couldnt be bothered.
This makes it easy to redifine, add, remove, or reorder individual rules. I reordered some of your rules and joined some other together, and I think I eliminated some possible bugs.
Last edited by gnud (2009-09-17 11:56:07)