When Using The Test Command ([]) In Bash, Don’t Forget To Put Spaces!

I had a tiny bug while I was trying to set up my image processing build process. I needed to check if a file exists so I did something like this:

if [ -f path/to/file];then
    #...
fi

Looks fine except I got an error saying that ] was missing even though it was there. Turns out that you need to put a space before and after the brackets because the brackets are an actual command, specifically test, like this:

if [ -f path/to/file ];then
    #...
fi

Subtle, but worth watching out for!