Shell Programming and Scripting

#!/bin/bash

echo "Enter the type of file: "
read f

a=(*.$f)

for (( i =0; i < ${#a[i]}; i++ ))
do
echo $i "  " ${a[i]}
done

echo "Enter the filenumber for processing:"
read j

cat ${a[$j]} | sed -e 's/\([[:punct:]]\)//g' > revised.txt

cat ${a[$j]} | sed -e 's/\([[:punct:]]\)//g' > revised.txt

sed -e 's/#/^g/g;s/\([[:punct:]]\)//g;s/^g/#/g' "${a[$j]}" > revised.txt

for i in $k
do
cat ${a[$j]} | sed 's/${k[$i]}/^g/g;s/\([[:punct:]]\)//g;s/^g/${k[$i]}/g' > revised.txt
done

declare -a k=('#' '@')

1) Not needed to say \([[:punct:]]\) as [[:punct:]] is all you need.
This makes the code a little simpler to view and understand.

$ cat punct.txt
Bb2~`!@#$%^&*()_-+={[}]|:;"'<,>.?/

$ cat punct.sh
mark=ZZZZZZZZZZZZZZZZZZZZ

echo "Deleting punctuation, except for :"
sed "s/:/$mark/g; s/[[:punct:]]//g; s/$mark/:/g" < punct.txt

echo "Deleting punctuation, except for ;"
sed "s/;/$mark/g; s/[[:punct:]]//g; s/$mark/;/g" < punct.txt

$ ./punct.sh
Deleting punctuation, except for :
Bb2:
Deleting punctuation, except for ;
Bb2;

$ cat punct.txt
Bb2~`!@#$%^&*()_-+={[}]|:;"'<,>.?/

$ cat punct.sh
echo "Deleting punctuation, except for @ and #"
rm -f s1.sed s2.sed control_file

echo "UNIQMARK01 @" >> control_file
echo "UNIQMARK02 #" >> control_file

while read mark sym; do
  echo "s/$sym/$mark/g" >> s1.sed
  echo "s/$mark/$sym/g" >> s2.sed
done < control_file

echo "s/[[:punct:]]//g" >> s1.sed
sed -f s1.sed -f s2.sed < punct.txt

rm -f s1.sed s2.sed control_file

$ ./punct.sh
Deleting punctuation, except for # and @
Bb2@#