commit 79724ccf0844a2baed7c2fa3cd39d5d1e32d7d8c
parent 89f7ffc4e7f9c7ffd838bd5e6bd35407b345c862
Author: FIGBERT <figbert@figbert.com>
Date: Thu, 21 Jan 2021 15:20:07 -0800
Add "My First RegEx" post
Diffstat:
1 file changed, 55 insertions(+), 0 deletions(-)
diff --git a/content/posts/my-first-regex.md b/content/posts/my-first-regex.md
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+title = "My First RegEx"
+description = "Yesterday, I wrote my first regular expression. I’ve always regarded regex as an arcane art of true shell wizards – and for the most part, I still do. Now though, I’ve gotten a glimpse of their world."
+date = 2021-01-21
++++
+
+`(?<=\.\/IssuerIcons\/).*(?=\.png)`
+<!-- more -->
+
+## What it does
+
+Let's break it apart piece by piece. It's meant to return the filename
+from a given path in a specific format. When given
+`./IssuerIcons/Example.png`, the script should return `Example`.
+
+The first section is a positive lookbehind: `(?<=\.\/IssuerIcons\/)`.
+This asserts that the selected portion must by preceeded by
+`./IssuerIcons/`.
+
+The section section is a pattern match: `.*`. This matches all
+characters, excluding newlines, of any length.
+
+The third and final section is a positive lookforward: `(?=\.png)`.
+This asserts that the selected portion must be followed by `.png`.
+
+## Background
+
+Yesterday, I wrote my first regular expression. I've always regarded
+regex as an arcane art of true shell wizards – and for the most part,
+I still do. Now though, I've gotten a glimpse of their world.
+
+I wrote this expression for [Tofu][tofu], an open-source 2FA app for
+iOS. I had been thinking of making more "issuer icons" for the app
+when I noticed that the icons were all designed in one Sketch file.
+This could become a problem if two people were to edit the file at
+one time, so I suggested a [solution][issue].
+
+The author got back to me with another idea: ditch Sketch altogether,
+and replace it with a shell script that generates icons from a
+directory of `png`s. I [wrote it][pr]. I've since refined it, with
+help from [ThinkChaos][tc], to make it independent of any preceding
+directories using `sed`: `sed -E 's:.+/(.+)\.png:\1:'`.
+
+It was a really fun experience – I've never written bash before! It
+reminded me a lot of Drew DeVault's post [Become shell literate][sl].
+I work primarily from my terminal, and am slowly working my way up to
+true mastery – I'm nowhere near close, but this was a step in the right
+direction.
+
+[tofu]: https://www.tofuauth.com/
+[issue]: https://github.com/calleerlandsson/Tofu/issues/52
+[pr]: https://github.com/calleerlandsson/Tofu/pull/60
+[sl]: https://drewdevault.com/2020/12/12/Shell-literacy.html
+[tc]: https://github.com/ThinkChaos
+
