I’ve been reading Mastering Regular Expressions by Jeffrey E.F. Friedl, and since nobody in my life (aside from my wife) cares, I thought I’d share something I’m pretty proud of. My first set of regular expressions, that I wrote myself to manipulate the text I’m working with.

What’s I’m so happy about is that I wrote these expressions. I understand exactly what they do and the purpose of each character in each expression.

I’ve used regex in the past. Stuff cobbled together from stack overflow, but I never really understood how they worked or what the expressions meant, just that they did what I needed them to do at the time.

I’m only about 10% of the way through the book, but already I understand so much more than I ever did about regex (I also recognize I have a lot to learn).

I wrote the expressions to be used with egrep and sed to generate and clean up a list of filenames pulled out of tarballs. (movies I’ve ripped from my DVD collection and tarballed to archive them).

The first expression I wrote was this one used with tar and egrep to list the files in the tarball and get just the name of the video file:

tar -tzvf file.tar.gz | egrep -o '\/[^/]*\.m(kv|p4)' > movielist

Which gives me a list of movies of which this is an example:

/The.Hunger.Games.(2012).[tmdbid-70160].mp4

Then I used sed with the expression groups to remove:

  • the leading forward slash
  • Everything from .[ to the end
  • All of the periods in between words

And the last expression checks for one or more spaces and replaces them with a single space.

This is the full sed command:

sed -Eie 's/^\///; s/\.\[[a-z]+-[0-9]+\]\.m(p4|kv)//; s/[^a-zA-Z0-9\(\)&-]/ /g; s/ +/ /g' movielist

Which leaves me with a pretty list of movies that looks like this:

The Hunger Games (2012)

I’m sure this could be done more elegantly, and I’m happy for any feedback on how to do that! For now, I’m just excited that I’m beginning to understand regex and how to use it!

Edit: fixed title so it didn’t say “regex expressions”

  • DefederateLemmyMl@feddit.nl
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    10 months ago

    You are strawmanning, and your links are not countering any point I made. I never disputed the depreciation as fact, and I never recommended that beginners should use egrep over grep -E

    I disputed your claims that the egrep command has just been a distro hack all these years, when in fact GNU to this day still distributes egrep through its source tarballs and only very recently started to warn about it through the wrapper script. And again, the only “portability problem” here is the fact that they deprecated it in the first place, i.e. a self-inflicted one.

    Then as a Linux and Unix veteran I gave my subjective opinion by lamenting and criticizing the fact that this depreciation happened, and how changes like this always feel like unnecessary pedantry to me. Yes it’s an expression of frustration, but I am allowed to feel frustrated about it. I don’t need people like you invalidating how I feel about breaking changes in software that I use daily.