Match a single character in a string bash script

Question

My issues is that I want to read a character from the stdin and compare it with a string value. If that character exists then I want to display a message. Eg, saving % into the variable $a:

$ read a
%
$echo $a
%

There is variable defined say v='~`!@#$%^&*()_-+=:;{[}]|\/<>,."' all possible special character including single tick '

I need to check if the character input exists in the string value. How can I do this.

Answer 1

case $v in
  *"$a"*) printf '<%s> is in <%s>\n' "$a" "$v"
esac

Answer 2

Here you go:

#!/bin/bash
v='~`!@#$%^&*()_-+=:;{[}]|/<>,."'
echo type any character and press enter
IFS= read -r a
[[ $v =~ "$a" ]] && echo match || echo not

Answer 3

Try this

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