Bourne Shell Debugger Shows a Shell Variable (Unix Power Tools, 3rd Edition)

37.2. 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 for variable names and displays their values (Section 36.14):

% 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 (Section 27.8) 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.

-- JP