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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 [ $CHOICE -eq 1 ]; My question here is, why is the space around the square brackets so important in Bash?
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The lack of spaces is actually how the shell distinguishes an assignment from a regular command. Also, spaces are required around the operators in a [ command: [ "$timer"=0 ] is a valid test command, but it doesn't do what you expect because it doesn't recognize = as an operator.
Bash indenting is very sensitive to characters. For example a space behind “do” in while/for loops will throw it of. When you have nested loops this is very ugly, and makes it hard to follow the code.
To cd to a directory with spaces in the name, in Bash, you need to add a backslash ( \ ) before the space. In other words, you need to escape the space.
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.
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.
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