What is $opt variable for command line parameter in bash

Question

I have below bash script, I am a bit confuse about what is $opt meaning. and I do not find detail information about it after search.

test.sh:

echo

Answer 1

$opt is not a built-in or special variable. If it's mentioned in the script (outside of for opt without the in something part, which @mhawke already explained) it should either be defined earlier in the script or it's expected that it is exported before running the script.