Why am i getting an unexpected operator error in bash string equality test? [duplicate]

Question

Where is the error on line four?

if [ $bn == README ]; then

which i still get if i write it as

if [ $bn == README ]
then

or

if [ "$bn" == "README" ]; then

Context:

for fi in  /etc/uwsgi/apps-available/* 
do 
        bn=`basename $fi .ini`
        if [ $bn == "README" ]
        then
                echo "~ ***#*** ~"
        else
                echo "## Shortend for convience ##"
        fi
done

Answer 1

You can't use == for single bracket comparisons ([ ]). Use single = instead. Also you must quote the variables to prevent expansion.

if [ "$bn" = README ]; then

If you use [[ ]], that could apply and you wouldn't need to quote the first argument:

if [[ $bn == README ]]; then

Answer 2

Add the following to the top of your script:

#! /bin/bash

In bash, == is the same as = when used inside of single brackets. This is, however, not portable. So you should explicitly tell the shell to use bash as the script's interpreter by putting #! /bin/bash at the top of the script.

Alternatively, do your string comparisons using =. Note that the == operator behaves differently when used inside of double-brackets than when inside of single-brackets (see the link).