Add Reference The Full Match In The Replacement as a Sed TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://visualmode.kit.com/newsletter).
 
-_1703 TILs and counting..._
+_1706 TILs and counting..._
 
 See some of the other learning resources I work on:
 
@@ -1413,6 +1413,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [List The Running Ruby Version](ruby/list-the-running-ruby-version.md)
 - [Listing Local Variables](ruby/listing-local-variables.md)
 - [Make An Executable Ruby Script](ruby/make-an-executable-ruby-script.md)
+- [Make Structs Easier To Use With Keyword Initialization](ruby/make-structs-easier-to-use-with-keyword-initialization.md)
 - [Map With Index Over An Array](ruby/map-with-index-over-an-array.md)
 - [Mock Method Chain Calls With RSpec](ruby/mock-method-chain-calls-with-rspec.md)
 - [Mocking Requests With Partial URIs Using Regex](ruby/mocking-requests-with-partial-uris-using-regex.md)
@@ -1499,6 +1500,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [OSX sed Does Regex A Bit Different](sed/osx-sed-does-regex-a-bit-different.md)
 - [Output Only Lines Involved In A Substitution](sed/output-only-lines-involved-in-a-substitution.md)
 - [Reference A Capture In The Regex](sed/reference-a-capture-in-the-regex.md)
+- [Reference The Full Match In The Replacement](sed/reference-the-full-match-in-the-replacement.md)
 - [Use An Alternative Delimiter In A Substitution](sed/use-an-alternative-delimiter-in-a-substitution.md)
 
 ### Shell
@@ -1716,6 +1718,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Produce A Lowercase V4 UUID](unix/produce-a-lowercase-v4-uuid.md)
 - [Provide A Fallback Value For Unset Parameter](unix/provide-a-fallback-value-for-unset-parameter.md)
 - [Remove A Directory Called `-p`](unix/remove-a-directory-called-dash-p.md)
+- [Rename A Bunch Of Files By Constructing mv Commands](unix/rename-a-bunch-of-files-by-constructing-mv-commands.md)
 - [Repeat Yourself](unix/repeat-yourself.md)
 - [Replace Pattern Across Many Files In A Project](unix/replace-pattern-across-many-files-in-a-project.md)
 - [Run A Command Repeatedly Several Times](unix/run-a-command-repeatedly-several-times.md)

ruby/make-structs-easier-to-use-with-keyword-initialization.md

@@ -0,0 +1,44 @@
+# Make Structs Easier To Use With Keyword Initialization
+
+Typically a [`Struct`](https://ruby-doc.org/3.4.1/Struct.html#method-c-new) in
+Ruby is defined and initialized like so:
+
+```ruby
+> Subscriber = Struct.new(:email, :first_name, :status, :tags)
+=> Subscriber
+> s1 = Subscriber.new('bob.burgers@example.com', 'Bob', :active, [:food, :family])
+=> #<struct Subscriber email="bob.burgers@example.com", first_name="Bob", status=:active, tags=[:food, :family]>
+> s1.email
+=> "bob.burgers@example.com"
+```
+
+That's a nice way to structure light-weight objects.
+
+A potential challenge with multi-argument `Struct` definitions like this,
+especially when they aren't colocated with initialization, is that it can be
+hard to remember or distinguish the argument order when initializing an instance
+of one.
+
+Ruby 2.5 added the `keyword_init` option to help with this exact issue. When
+that option is set to `true` for a `Struct` definition, then we get to
+initialize it with keyword arguments rather than positional arguments.
+
+```ruby
+> Subscriber = Struct.new(:email, :first_name, :status, :tags, keyword_init: true)
+=> Subscriber(keyword_init: true)
+* s1 = Subscriber.new(
+*   first_name: 'Bob',
+*   email: 'bob.burgers@example.com',
+*   tags: [:food, :family],
+*   status: :active
+> )
+=> #<struct Subscriber email="bob.burgers@example.com", first_name="Bob", status=:active, tags=[:food, :family]>
+> s1.email
+=> "bob.burgers@example.com"
+```
+
+Notice I have to use keyword arguments now and that because of that I can
+organize them in whatever order makes sense. Coming back to view this line of
+code later, it is easy to see attribute each value corresponds to.
+
+[source](https://www.bigbinary.com/blog/ruby-2-5-allows-creating-structs-with-keyword-arguments)

sed/reference-the-full-match-in-the-replacement.md

@@ -0,0 +1,27 @@
+# Reference The Full Match In The Replacement
+
+The `&` can be used in the replacement part of a `sed` expression as reference
+to the string match for this iteration of the expression. The occurrence of `&`
+will be replaced with that entire match.
+
+As the `sed` man page puts it:
+
+> An ampersand (“&”) appearing in the replacement is replaced by the string
+> matching the RE.
+
+I made use of this recently with [a `sed` expression that was evaluating a list
+of filenames that I wanted to construct into a sequence of `mv`
+commands](unix/rename-a-bunch-of-files-by-constructing-mv-commands.md). I needed
+the filename that I was matching on to appear as the first argument of the `mv`
+command I was constructing.
+
+Here is what that looks like:
+
+```bash
+$ ls *.pdf |
+  sed 's/\(..\)\(..\)\(..\) Statement\.pdf/mv "&" "20\3-\1-\2-statement.pdf"/'
+```
+
+Notice right after `mv` in literal quotes is the `&`. That will be replaced in
+the resulting replacement with the full matching string of the regular
+expression in the first part of the sed statement (`s/<RE>/`).

unix/rename-a-bunch-of-files-by-constructing-mv-commands.md

@@ -0,0 +1,51 @@
+# Rename A Bunch Of Files By Constructing mv Commands
+
+I downloaded a bunch of bank statements as PDFs. On the upside they all were
+consistently named. On the downside they used an unhelpful date format. With a
+date format that puts year before month before day, the files easily sort
+alphanumerically. However, these filenames used a date format that put month
+before day before year.
+
+Here is a subset of the files
+
+```bash
+$ ls *.pdf
+'012524 Statement.pdf'
+'012725 Statement.pdf'
+'022624 Statement.pdf'
+'022625 Statement.pdf'
+'032524 Statement.pdf'
+'032525 Statement.pdf'
+```
+
+Notice they are named with `MMDDYY Statement.pdf`. I would instead like for them
+to be named as `YYYY-MM-DD-statement.pdf`.
+
+I can generate a series of `mv` statements that then get piped to `sh` which
+_evaluates_ them. But first, let's do a dry run of a `sed` statement that
+rearranges the date parts.
+
+```bash
+$ ls *.pdf | sed 's/\(..\)\(..\)\(..\) Statement\.pdf/mv "&" "20\3-\1-\2-statement.pdf"/'
+mv "012524 Statement.pdf" "2024-01-25-statement.pdf"
+mv "012725 Statement.pdf" "2025-01-27-statement.pdf"
+mv "022624 Statement.pdf" "2024-02-26-statement.pdf"
+mv "022625 Statement.pdf" "2025-02-26-statement.pdf"
+mv "032524 Statement.pdf" "2024-03-25-statement.pdf"
+mv "032525 Statement.pdf" "2025-03-25-statement.pdf"
+```
+
+The way this works is that all the `pdf` files in the current directly get
+listed out. That gets piped to a `sed` statement that matches on capture groups
+against the first three pairs of characters (the date parts) in the filenames.
+It matches on the rest of the filename (` Statement.pdf`). This is then replaced
+by a `mv `, the full match of the original filename (`&`), and then the new
+filename made up of the rearranged date parts.
+
+I can then pipe it to `sh` to run those `mv` commands.
+
+```bash
+$ ls *.pdf |
+  sed 's/\(..\)\(..\)\(..\) Statement\.pdf/mv "&" "20\3-\1-\2-statement.pdf"/' |
+  sh
+```