Add Grab All The Method Names Defined In A Ruby File as a sed til

sed/grab-all-the-method-names-defined-in-a-ruby-file.md

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+# Grab All The Method Names Defined In A Ruby File
+
+I wanted a listing of all the methods defined in a Ruby file. Metaprogramming
+aside, I figured I could write a one-line `sed` script to effectively do this.
+
+```bash
+$ sed -n 's/[[:space:]]*def \([[:alnum:]_?!]*\).*/\1/p' file.rb
+```
+
+Let's break this down.
+
+- `[[:space:]]*` accounts for any level of indentation.
+- `def ` matches againts the start of a method definition.
+- `\(...\)` is a capture that can be referenced in the replace side of the
+  script.
+- `[[:alnum:]_?!]*` represents the characters that can make up a Ruby method
+  name, this is equivalent to writing `[a-zA-Z0-9_?!]*`.
+- `.*` is the final part of the regex match which ensures the rest of the line
+  is loaded into the pattern space so that the replacement will only be the
+  method name.
+- `\1` replaces everything in the first part of the script with the capture
+  which is just the method name.
+- combining the `-n` and `p` flags ensures that only lines with substitutions
+  are printed.
+
+This probably isn't perfect, but it is good enough to reference from time to
+time in my shell history.