Question

I have this piece of code:

if(("$op" == "q")); then

which throws out this error:

l5p3.sh: line 10: ((: + == q: syntax error: operand expected (error token is "== q")

what’s the issue? How to compare $op with the letter $q ?

Answer 1

(( ... )) (for arithmetic expressions) is probably not what you want. Check the following:

if (("asd" == "bla")); then
  echo test
else
  echo bah
fi

It prints test in Bash and an error in a strictly bourne-compatible shell like dash.

Try the following instead:

if [[ $op == q ]]; then