Control-C vs Control-D

When starting to use the terminal, it’s inevitable that you come across running a command that remains running and the direction is to press Control-C to stop it.

And sometimes, you may be directed to press Control-D.

But what’s the difference? Why did one work one time and not the other?

A simple question you can ask yourself:

Has the command prompted for input?

Demonstration time

So, does this command prompt for input?

$ npm start

> school-locator@0.1.0 start /Users/travis/work/tps/school-locator
> react-scripts start

Starting the development server...

Compiled successfully!

You can now view school-locator in the browser.

  Local:            http://localhost:3001/
  On Your Network:  http://192.168.1.65:3001/

No. It’s just a running development server. So Control-C.

^C

Think of it as “Cancel”.

Let’s try another.

Does this command prompt for input?

$ pgcli

Server: PostgreSQL 13.0
Version: 3.0.0
Chat: https://gitter.im/dbcli/pgcli
Home: http://pgcli.com
travis@/tmp:travis>

Yes. It’s expecting me to input some SQL queries. So Control-D.

^D
Goodbye!

I don’t have a handy mnemonic but I remember it as part of the C/D pair.

To re-enforce using Control-D to quit a prompt, consider a typical terminal: It’s a prompt, and waiting for your input.

$

^D

My iTerm2 window closed. But Terminal.app may just say:

[Process completed]

Summary

• Control-C if it’s just running, doing it’s thing.
• Control-D if it’s waiting on you.

References

• Control-C
• Control-D
• ASCII control codes
• iTerm2
• Terminal.app
• pgcli