[plug] Bash Ctrl+S

[Onno Benschop]

While I don't have a definitive answer to the Ctrl-S history, I seem to
recall it's about suspending output, originally to a physical line printer,
(and a teletype before that), but don't quote me on that.

I came across a discussion on Mastodon about other bash tricks and tips:

https://infosec.exchange/@cR0w/116915966560002695


--
finger painting on glass is an inexact art - apologies for any errors in
this scra^Hibble

()/)/)() ..ASCII for Onno..



On Thu, 16 July 2026, 18:27 Juneidy Wibowo via plug, <plug at plug.org.au>
wrote:

> G'day all,
>
> Sharing a revelation that I had today, that might sound obvious to long
> time linux users.
>
> I am by no means a linux newbie, but nevertheless, I am always learning
> something new about GNU/Linux.
>
> I am a primarily terminal user and I have always used terminal multiplexer
> like GNU-screen and tmux.
>
> Occasionally, I would use the "copy mode" of the multiplexer to "freeze"
> the screen to copy a few stuff. And the string I want to copy can be a long
> JSON string that line wraps in my terminal.
>
> Now if you use a mouse to highlight and copy this long string while in the
> multiplexer's "copy mode", the line wraps translates to a "new line" (\n)
> character.
>
> So occasionally, I would use Ctrl+S to maintain the line wrap of this long
> string to copy, then continue with Ctrl+Q when I am done.
>
> Here's the part that I never noticed and surprised me today: bash actually
> "freezes" the process while in this mode provided if the process writes to
> /dev/stdout​.
>
> I did a few tests with some simple for-loop in bash:
>
> $ for i in {1..20}; do date >> /tmp/foo.log; sleep 1; done # Does not
> freeze the process with ctrl+s
>
> Whereas
>
> $ for i in {1..20}; do date >> /tmp/foo.log; date; sleep 1; done # Freezes
> the process with ctrl+s​
>
> I guess this only came as a surprise because I am so used to terminal
> multiplexer "copy mode" where the process continues to produce output while
> in this mode and you are fast-forwarded after you exited "copy mode".
>
> I haven't really bothered to find out the history of this Ctrl+S but
> someone smarter than I am might shed some wisdom/history on this.
>
> Regards,
> Juneidy
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