[plug] Bash Ctrl+S

[Juneidy Wibowo]

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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