Every day pretty much with Unix tools. Vim, awk, sed, etc.

On average I’ve probably had to work with them or write one from scratch only a handful of times per year over my career. Not often enough to be an expert or anything but I’m not so afraid of them as I used to be.

Actually writing code that uses them: last month. Commandline: last week.

I used it to check a user input format.

Yesterday, for capturing URLs.

Today.

At least once every few days while coding, usually to do one of the following:

1. Select multiple things in the same file at the same time without needing to click all over the place

   Normally I use multicursor keyboard shortcuts to select what I want and for the trickier scenarios there are also commands to go through selections one at a time so you can skip certain matches to end up with only what you want.

   But sometimes there are too many false matches that you don’t want to select by hand and that’s where regex comes in handy.

   For instance, finding:

   • parent but not apparent, transparent, parentheses, apparently, transparently
   • test but not latest, fastest, testing, greatest, shortest
   • trie but not entries, retries, countries, retrieve
   • http but not https

   … which can be easily done by searching for a word that doesn’t include a letter immediately before or immediately after: e.g. \Wtest\W.

2. Search for things across all files that come back with too many results that aren’t relevant

   Basically using the same things above.

3. Finding something I already know makes a pattern. Like finding all years: \d{4}, finding all versions: \d+\.\d+\.\d+, finding random things that a linter may have missed such as two empty lines touching each other: \n\s*\n\s*\n, etc…

Asking this question is like asking when was the last time you had to search through text.

This sentence is the uncanny valley for structure.

We use it for triaging test failure (running tens of thousands of tests for CPU design verification).

That use is acceptable because it is purely informational. In general you should avoid regexes at all costs. They’re difficult to read, and easy to get wrong. Generally they are a very big red flag.

Unfortunately they tend to get used where they shouldn’t due to lazy developers not parsing things properly.