In /usr/bin/espdiff line 47:
	recurse=1
        ^-----^ SC2034: recurse appears unused. Verify use (or export if used externally).


In /usr/bin/espdiff line 51:
	compare=1
        ^-----^ SC2034: compare appears unused. Verify use (or export if used externally).


In /usr/bin/espdiff line 68:
  if [ $? -ne 0 ]
       ^-- SC2181: Check exit code directly with e.g. 'if mycmd;', not indirectly with $?.


In /usr/bin/espdiff line 78:
  delay=$(($delay * 2))
           ^----^ SC2004: $/${} is unnecessary on arithmetic variables.


In /usr/bin/espdiff line 81:
read -t $delay -p 'Please concentrate... ' || echo
^--^ SC2162: read without -r will mangle backslashes.

For more information:
  https://www.shellcheck.net/wiki/SC2034 -- compare appears unused. Verify us...
  https://www.shellcheck.net/wiki/SC2162 -- read without -r will mangle backs...
  https://www.shellcheck.net/wiki/SC2004 -- $/${} is unnecessary on arithmeti...