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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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Linux Terminal: CTRL+D is like pressing ENTER (hackarcana.com)

submitted 5 days ago by tuna@discuss.tchncs.de to c/linux@lemmy.ml

18 comments fedilink hide all child comments

Honestly I had no idea what ctrl+d even did, I just knew it was a convenient way for me to close all the REPL programs I use. The fact that it is similar to pressing enter really surprised me, so I wanted to share this knowledge with you :)

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[–] double_quack@lemm.ee 18 points 5 days ago* (last edited 5 days ago) (5 children)

Ctl-D is the End-of-File character. Programs interpret it as "that's it, the input you were reading has finished", and react accordingly.

[–] tuna@discuss.tchncs.de 4 points 5 days ago (4 children)

$ cat
You sound very nice :)
You sound very nice :)
Bye<ctl-d>Bye

Oh wait, and cool too
Oh wait, and cool too
<ctl-d>
$

The Ctl-D didn't end the file when i typed "Bye" :( it only worked when I pressed Ctl-D on its own line. So how does cat know that it should ignore the EOF character if there is some text that comes before it?

What Ctl-D does is flush the input to the program, and the program sees how big that input is. If the length of the input is 0 that is interpreted as EOF. So Ctl-D is like Enter because they both flush the input, but Ctl-D is unlike Enter because it does not append a newline before flushing, and as a consequence you can send empty input (aka an EOF "character") with Ctl-D.

[–] skepller@lemmy.world 0 points 5 days ago* (last edited 5 days ago)

This!

It's merely a buffer flush, in case it's empty, the program handling the input can choose how to interpret, cat decides to do it as an EOF.

Reason why it also works as exit.

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