I hadn't noticed that the first line of your script contains a leading <space> character before the #!/bin/bash, so RudiC is probably correct in saying that that is why your script wasn't run using bash as its interpreter. Unless #!interpreter_path starts in column 1 on the 1st line in your file, that line is just a comment and has absolutely no effect on what interpreter will be used to run your script.

You haven't told us what operating system you're using, but it looks like the default shell on your is a Bourne shell or something like dash that doesn't include a lot of the bells and whistles provided by shells like bash and ksh that are extensions above and beyond what is required by the POSIX standards.

In POSIX-conforming shells the command:

Code:

[ expression ]

is a synonym for the command:

Code:

test expression

and there is no specification of what:

Code:

[[ expression ]]

does. The test and [ commands are utilities and they are often built-in into the shell as well as being available as stand-alone utilities. The [[ expression ]] is not a utility; it is a part of the syntax of those shells that provide this extension.

So, using [ "$var" = "string" ] is portable to a wide range of shells. And on shells that support [[ "$var" == "string" ]], it is often a little bit faster, often supports more operators than test, and has different requirements for when double-quotes are required and how shell variables are expanded.

I'm glad my sample case statement helped you figure out how it works. We're here to help you learn how to use the tools that are available to you on UNIX, Linux, and similar systems.