this post was submitted on 09 Feb 2024
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I read a lot of answers online that its a bad idea, but the arguments did not make a lot of sense. "it's a heavily ingrained part of the eco system". Well if I can change it, what's the deal?

It makes more sense to make an interrupt signal be the harder shortcut, and copy to be ctrl+C, matching other programs and platforms.

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[–] [email protected] 273 points 8 months ago* (last edited 8 months ago) (6 children)

matching other programs and platforms

Actually, Ctrl+C is the interrupt hotkey for pretty much every CLI app/terminal on every platform. Try it within the Command Prompt/PowerShell/Windows Terminal, or the macOS terminal - they'll all behave the same.

The use of Ctrl+C as an interrupt/termination signal has a very long history even predating the old UNIX days and DEC - it goes back to the days of early telecommunications, where control characters were used for controlling the follow of data through telecommunication lines. These control characters, along with regular characters, were transmitted by being encoded in binary, and this encoding scheme was defined by ASCII (American Stanard Code for Information Interchange), published in 1963.

In ASCII, the control character ETX (meaning end-of-text; represented by the hex code 0x03) was used to indicate "this segment of input is over", or "stop the current processing".

Now what does all this have to do with with Ctrl+C you ask?

For that, you'll need to go back to the days of early keyboards. Keyboards back then generated ASCII codes directly, and when a modifier key (Ctrl/Shift/Meta) on a keyboard was pressed in combination with another key, it modified the signal sent by the keyboard to produce a control character.

Specifically, pressing Ctrl with a letter key made the keyboard clear (set to zero) the upper three bits of the binary code of the letter, thus effectively mapping the letter keys to control characters (0x00 - 0x1F: the first 32 characters on the ASCII table).

  • The ASCII code for 'C' is 0x43 (binary 01000011).
  • Pressing Ctrl+C clears the upper three bits, resulting in 00000011, which is 0x03 in hex.

And would you look at that, 0x03 is the code which represents the control character ETX.

The use of ETX to interrupt a program in digital computers was first adopted by the TOPS-10 OS, which ran on DEC's PDP-10 computer, back in the late 60s. It's successor, TOPS-20 also included it, followed by the RSX-11 (on the PDP-11), and VMS (on the VAX-11).

RSX-11 was a very influential OS, created by a team that included David Cutler. It influenced the design of several OSes that followed, such as VMS and Windows NT. Cutler later moved to Microsoft and became the father of Windows NT. Early NT did not include a GUI, so it was natural to adopt existing terminal operation standards, including the use of ETX. In fact, NT's internals were so similar to VMS that a lawsuit was in the works, but instead, MS agreed to pay off DEC millions of $$$.

Also, when UNIX first came out (1969), it ran on DEC hardware, and so they followed the tradition of using the ETX signal to stop programs. This convention flowed to BSD (1978) which was based on UNIX, and NeXTSTEP (1989), which was based on BSD. NeXTSTEP was developed by NeXT Computers, which was founded by Steve Jobs... and the rest is history.

Therefore, Ctrl+C is something that's deeply rooted in history. You don't just simply change something like that. Sure, you may be able to remap the keybindings, but it's actually hardcoded into many programs so you'll run into inconsistencies - that is, if you used the standard remapping tools built into GNOME/KDE etc.

If you want to truly remap Ctrl+C, you'll want to do so at a lower level (evdev layer) so that it's not intercepted by other programs, eg using tools like evremap or keyd. But even then, it's not guaranteed to work everywhere, for instance, if you're inside a VM or using a different OS, or in a remote session. So it's best to remap the keys at the keyboard layer itself, which is possible on many popular mechanical keyboards using customisable firmware like QMK/VIA.

[–] [email protected] 38 points 8 months ago

Outstanding post. It has depth and is presented in compelling language.

[–] [email protected] 29 points 8 months ago

Best comment I’ve read on Lemmy in weeks. Thought provoking, enlightening, and incredibly well written. Thank you for hanging out here.

[–] [email protected] 16 points 8 months ago

Bravo, very good explanation! As fun fact, i still have at work several DEC ALPHA and OpenVMS servers (some are now VM but we still have physical servers from this era managing our data) and Ctrl+C works well!

[–] [email protected] 3 points 8 months ago

Switching it at the terminal emulator level should work fine for every CLI/TUI though, right? Just have your terminal send 0x03 when you press C-S-c and copy selected text on C-c. I haven't tested it but I'm sure that alacritty, wezterm, windows terminal and probably tmux can do this.

[–] [email protected] 2 points 8 months ago

Great post, thanks!

[–] [email protected] 1 points 8 months ago

I will point out that in modern Windows terminals, Ctrl+C does copy selected text if there's text selected; personally, I don't see a problem with having it be context aware like that to make it behave more like how the majority of current users will be expecting based on how programs outside the CLI behave