GNU Readline is Underappreciated
Today I want to give a shout out to what I am realizing is a very underappreciated piece of software: GNU Readline. If you have ever used Bash, you’ve used Readline. It is a library for powering command line interfaces. On the developer side, it makes it easy to add a nicely featured command prompt to your program.
On the user side of things, the benefit is not any specific feature, but simply the fact that it is popular and influential. There are other line editing libraries out there1, many of which copy the user interface it provides. It’s commands are a de-facto standard.
The result is that I can learn a few keybindings for bash, and then use them in python’s interpreter, use them in sqlite’s CLI. I can install a new debugger and the same keybindings Just Work™ without even needing to glance at the documentation.
I don’t even use all the standard commands. It only takes a few to greatly improve your experience. The main ones I use are:
- Ctrl-R: search backward through the history.
- Ctrl-A: Move the cursor to the beginning of the line.
- Ctrl-E: Move the cursor to the end of the line.
- Ctrl-K: delete from the cursor to the end of the line.
As a bonus these are all taken from Emacs, so now you know a little of that too if you ever try it2.