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+---
+title: Write programs that do one thing and do it well
+date: 2024-03-23
+permalink: archive/2024/03/23/write-programs-that-do-one-thing-and-do-it-well
+tags:
+    - software-development
+    - unix
+    - linux
+cta: ~
+snippet: |
+    Write programs that do one thing and do it well.
+---
+
+Over the last few days, I've written about watchers and running commands such as automated tests when files are changed.
+
+Some tools have this built in, whilst others don't.
+
+I've used different tools to do this and recently switched to `entr`.
+
+The previous one wasn't showing me the output from running Drupal automated tests, which `entr` does.
+
+I also like that it follows the UNIX philosophy of doing one thing well and working well with other programs.
+
+For example, to run my automated tests when I change a file, I need to run `find web/modules/custom | entr ./run test`.
+
+`entr` isn't concerned with how to find the list of files to watch - only what to do with them.
+
+To get the list of files, I use the `find` command and provide the files to `entr`.
+
+I also like to do this with my application code. I like to write small modules and libraries with clear boundaries and responsibilities, do their tasks well, and work well with other parts of the application.