if statement - Why should there be spaces around '[' and ']' in Bash?

Question

I was trying to write a Bash script that uses an if statement.

if[$CHOICE -eq 1];

The script was giving me errors until I gave a space before and after [ and before ] as shown below:

if [ $CHOICE -eq 1 ];

My question here is, why is the space around the square brackets so important in Bash?

Answer 1

Once you grasp that [ is a command, a whole lot becomes clearer!

[ is another way to spell "test".

help [

However while they do exactly the same, test turns out to have a more detailed help page. Check

help test

...for more information.

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Furthermore note that I'm using, by intention, help test and not man test. That's because test and [ are shell builtin commands nowadays. Their feature set might differ from /bin/test and /bin/[ from coreutils which are the commands described in the man pages.