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"cat readme.txt" is not safe if you use iTerm2

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Re: "cat readme.txt" is not safe if you use iTerm2

#191

Post by boomlinde »

em-bee wrote: post #168
boomlinde wrote: post #99

Earlier quoted context omitted.

> X11 or any network transparent graphics protocol doesn't solve the problems that a terminal solves. how do you pipe data through multiple applications in one command using a GUI for example? nobody has been able to solve that in a practical way yet. It seems to me that you are conflating the role of the terminal with the role of the shell. The terminal accepts streams of text and commands to instruct the terminal,…

i am not conflating them, the problem is rather that the current terminals define or restrict what the shell can do. shells are being rewritten already. b they could not do what i want them to do without the terminals changing too, so the terminal needs to be next.

You can absolutely pipe programs together using a shell without a terminal. This also doesn't restric in any way the possibility to "output to some kind of graphical device/interface that uses that semantic information to display the data using nice graphical interface elements".

What is it specifically that you want to do which your favorite shell doesn't allow because it is restricted by terminals?

Re: "cat readme.txt" is not safe if you use iTerm2

#192

Post by em-bee »

boomlinde wrote: post #191
em-bee wrote: post #168

Earlier quoted context omitted.

i am not conflating them, the problem is rather that the current terminals define or restrict what the shell can do. shells are being rewritten already. b they could not do what i want them to do without the terminals changing too, so the terminal needs to be next.

You can absolutely pipe programs together using a shell without a terminal. This also doesn't restric in any way the possibility to "output to some kind of graphical device/interface that uses that semantic information to display the data using nice graphical interface elements". What is it specifically that you want to do which your favorite shell doesn't allow because it is restricted by terminals?

yes, i can write a program that takes data and displays it nicely. but in order to use graphics i need a second channel to send the graphic instructions, for x11, wayland or even MacOS or wndows. at that point i have two interfaces, the terminal and that graphics display. i want both to be in one. i want the terminal to be that graphical output. that currently is only possible through in-band escape sequences. that is the restriction i want to get rid of.

Re: "cat readme.txt" is not safe if you use iTerm2

#193

Post by skissane »

rep_lodsb wrote: post #122
skissane wrote: post #94

Earlier quoted context omitted.

This could be fixed with an extension to the kernel pty subsystem Allow a process to send control instructions out-of-band (e.g. via custom ioctls) and then allow the pty master to read them, maybe through some extension of packet mode (TIOCPKT) Actually, some of the BSDs already have this… TIOCUCNTL exists on FreeBSD and (I believe) macOS too. But as long as Linux doesn’t have it, few will ever use it Plus the FreeB…

For this use case, there would also have to be an extension to the SSH protocol to send such out-of-band information. Maybe this already exists and isn't used? The broader problem with terminal control sequences didn't exist on Windows (until very recently at least), or before that DOS and OS/2. You had API calls to position the cursor, set color/background, etc. Or just write directly to a buffer of 80x25 characters…

> For this use case, there would also have to be an extension to the SSH protocol to send such out-of-band information. Maybe this already exists and isn't used?

I don’t think one already exists, but it would be straightforward to create one. SSH protocol extensions are named by strings of form NAME@DNSDOMAIN so anyone can create one, registration would not be required.

The hardest part would be getting the patches accepted by the SSH client/server developers. But that’s likely easier than getting the feature past the Linux kernel developers.

Re: "cat readme.txt" is not safe if you use iTerm2

#194

Post by skissane »

m3047 wrote: post #179
skissane wrote: post #94

Earlier quoted context omitted.

This could be fixed with an extension to the kernel pty subsystem Allow a process to send control instructions out-of-band (e.g. via custom ioctls) and then allow the pty master to read them, maybe through some extension of packet mode (TIOCPKT) Actually, some of the BSDs already have this… TIOCUCNTL exists on FreeBSD and (I believe) macOS too. But as long as Linux doesn’t have it, few will ever use it Plus the FreeB…

Architecture Astronaut! TCP is a stream protocol. A terminal program is expected to honor the stream protocol: I can use a terminal program to speak SMTP or HTTP. I can paste binary shit into it and copy binary shit out of it (some caveats apply). If you're gonna jack some control protocol into a session which is sitting directly on the stream protocol, that's on you. This is as airtight as injecting a control protoc…

> TCP is a stream protocol

Which has nothing to do with terminals, because nobody runs terminals directly over TCP. Telnet wasn’t simply sending terminal bytes over TCP, it has its own complex system of escape sequences and protocol negotiation (IAC WILL/WONT/DO/DONT/SB/SE, numerous Telnet options). SSH is even further from raw TCP than Telnet was

And a Unix pty isn’t a simple stream either. Consider SIGWINCH

Re: "cat readme.txt" is not safe if you use iTerm2

#195

Post by boomlinde »

em-bee wrote: post #192
boomlinde wrote: post #191

Earlier quoted context omitted.

You can absolutely pipe programs together using a shell without a terminal. This also doesn't restric in any way the possibility to "output to some kind of graphical device/interface that uses that semantic information to display the data using nice graphical interface elements". What is it specifically that you want to do which your favorite shell doesn't allow because it is restricted by terminals?

yes, i can write a program that takes data and displays it nicely. but in order to use graphics i need a second channel to send the graphic instructions, for x11, wayland or even MacOS or wndows. at that point i have two interfaces, the terminal and that graphics display. i want both to be in one. i want the terminal to be that graphical output. that currently is only possible through in-band escape sequences. that i…

I don't fully understand the request. On one hand you don't want a second channel to send the graphics instructions, but on the other you don't want to use in-band escape sequences.

Maybe you'd be interested to learn about plan9's graphical terminal. Its window manager runs entirely within it, and all windows just represent multiplexed access to limited areas of the terminal.

Re: "cat readme.txt" is not safe if you use iTerm2

#196

Post by em-bee »

boomlinde wrote: post #195
em-bee wrote: post #192

Earlier quoted context omitted.

yes, i can write a program that takes data and displays it nicely. but in order to use graphics i need a second channel to send the graphic instructions, for x11, wayland or even MacOS or wndows. at that point i have two interfaces, the terminal and that graphics display. i want both to be in one. i want the terminal to be that graphical output. that currently is only possible through in-band escape sequences. that i…

I don't fully understand the request. On one hand you don't want a second channel to send the graphics instructions, but on the other you don't want to use in-band escape sequences. Maybe you'd be interested to learn about plan9's graphical terminal. Its window manager runs entirely within it, and all windows just represent multiplexed access to limited areas of the terminal.

On one hand you don't want a second channel to send the graphics instructions, but on the other you don't want to use in-band escape sequences

correct. the in-band sequences are dangerous and unwieldy. they don't convey enough information. they are a hack to work within the limitations if historical terminals. that's what this whole thread is about.

a separate graphics channel creates a separate window. then you have two windows. not good either. it needs to be one window, and considering that this window should be able to support multiple remote connections it needs to be local otherwise i would get a new window for each server i connect to. that works for some people, but not for me. and it needs to work through a single channel like ssh/mosh or another similar protocol and be forwardable.

so i want a third option. one approach is sending semantic data, letting the terminal interpret it and display it graphically. this is interesting because shells are already exploring semantic data. (elvish, murex, nushell, others...)

plan9 sounds interesting. i see several efforts to port aspects of it to linux. they all seem to have stalled. more work needs to be done here. that's what i am advocating.

Re: "cat readme.txt" is not safe if you use iTerm2

#197

Post by connorboyle »

collinfunk wrote: post #175
connorboyle wrote: post #63

If I were a GNU core utils maintainer, I would not be too happy with this post title

I am one of them. The title of the substack seems fine since it mentions "if you use iTerm2". The tweet has no mention of iTerm2 which makes it sound like an issue in 'cat', which is mildly annoying [1]. [1] https://x.com/calif_io/status/2045207168677503241

Thanks for all your work.

The post title on 2026-04-18 (when this HN post was made) did not include this qualification:

https://web.archive.org/web/20260418153857/https://blog.cali...

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