${file##*.} and ${file%.*} explanation?

[Katherine]

I'm new to bash scripting. I been using a nifty tool to get the basename and extention for a filename.

Example:

file=blarg.txt
echo ${file%.*}
> blarg
echo ${file##*.}
> txt

And of course I can replace the "." for any character or string. This is great for paths too.

However, I don't really understand the syntax as it is cryptic. And when my friends ask for an explanation, I just . Does anyone know what's going on with the ##* and %.*? Is there a terminology I can use to google a tutorial or more tools.

Thanks a head of time!
~Kat

[nmset]

It's about bash parameter expansion, it's built-in.

Search for 'Remove matching prefix pattern' and 'Remove matching suffix pattern'

There are many more parameter expansion.

man bash

[Freston]

Here's a good description of it: parameter substitution