Question

I have a kind of complicated string, the form is

"xxxp+NUMyyy"

where xxx, NUM, and yyy are all variable length, and '+' can be a mathematical operator, such as '-', '*', '/', or '='.

I am trying to figure out the best way to get what mathematical operator and number the user has entered.

I tried using combination of things like this:

    echo `expr match "tcp+111" '\([+-=*/]\)'`
    echo `expr match "tcp+111" '\(\+\-=\*/\)'`

Nothing has worked thus far. I'm thinking the easiest way to do such a thing is by using regular expressions, but maybe I'm wrong? What is a good way to do this?

Thank You.

example input: "tcjp-100" "p+1" "p+1:debug" "cp=11:v". I did forget to mention, before the operator there will always be the letter 'p'. In addition, 'xxx' and 'yyy' do not have to be present, but can be

Answer 1

You can use Bash's regex matching feature.

string="xxxp+3456yyy"
pattern="[^*/+-]*([*/+-]*)([[:digit:]]+).*"    # the hyphen must come last (or first, but after ^) in the character sets

[[ $string =~ $pattern ]]
echo "${BASH_REMATCH[1]}"    # operator
echo "${BASH_REMATCH[2]}"    # number