46.3 Bourne Shell Debugger Shows a Shell Variable

If you have a shell script that sets several variables and you want to show the value of one of them, you can add a loop that asks you forvariable names and displays their values : ( 45.19 )

% 

cat myscript


#!/bin/sh
   ...
while echo "Pick a variable; just RETURN quits: \c"
      read var
do
      case "$var" in
      "") break ;;
      *)  eval echo \$$var ;;
      esac
done

The loop prompts Pick a variable: , then reads a value; if you type an empty answer, the loop quits. Otherwise, the value of that variable is displayed; the eval ( 8.10 ) command scans the echo command line twice.

This tip isn't just good for debugging. It's good in any shell script where you need to show the value of a variable by typing its name.