Add Type Fewer Paths With Brace Expansion as a Unix TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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-_1517 TILs and counting..._
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@@ -1540,6 +1540,7 @@ _1517 TILs and counting..._
 - [Switch Versions of a Brew Formula](unix/switch-versions-of-a-brew-formula.md)
 - [Tell direnv To Load The Env File](unix/tell-direnv-to-load-the-env-file.md)
 - [Touch Access And Modify Times Individually](unix/touch-access-and-modify-times-individually.md)
+- [Type Fewer Paths With Brace Expansion](unix/type-fewer-paths-with-brace-expansion.md)
 - [Undo Changes Made To Current Terminal Prompt](unix/undo-changes-made-to-current-terminal-prompt.md)
 - [Undo Some Command Line Editing](unix/undo-some-command-line-editing.md)
 - [Unrestrict Where ripgrep Searches](unix/unrestrict-where-ripgrep-searches.md)

unix/type-fewer-paths-with-brace-expansion.md

@@ -0,0 +1,49 @@
+# Type Fewer Paths With Brace Expansion
+
+Bash has a feature called _brace expansion_ that allows us to do a kind of
+shorthand when writing out file paths. We can specify multiple variants
+comma-separated between curly braces and they'll each be expanded into separate
+arguments.
+
+It's easier to understand this by seeing it. If we type the following (don't
+hit `Enter` yet):
+
+```bash
+$ mkdir src/{one,two,three}
+```
+
+And then hit _Tab_:
+
+```bash
+$ mkdir src/one src/two src/three
+```
+
+Bash uses the portion in braces to expand into separate arguments. The part
+outside the braces gets reused for each. That's where we get some savings from
+typing out the same path each time.
+
+Here is another example where we use `mv` to rename a file deeply nested in our
+project:
+
+```bash
+$ mv projects/project1/src/app/utils/{names,constants}.js
+```
+
+We don't even have to _Tab_ it out. We can hit _Enter_ directly and `mv` gets
+both arguments.
+
+Similarly, how about we change the extension of our renamed file:
+
+```bash
+$ mv projects/project1/src/app/utils/constants.{js,ts}
+```
+
+I've always found this feature most useful with paths and filenames, but you
+can do brace expansion with any arguments.
+
+```bash
+$ echo 1{3,1,6,4,9,2,7,5}
+13 11 16 14 19 12 17 15
+```
+
+[source](https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html)