Linux Crash Course - Data Streams (stdin, stdout & stderr)

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In this episode of Linux Crash Course, we'll go over data streams. Specifically, Standard Output (stdout), Standard Input (stdin), and Standard Error (stderr). We'll also take a look at how to redirect specific data streams, so you can easily separate errors from output.

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*⏰ TIME CODES*
00:00 - Intro
00:41 - Quick note regarding input/output
01:17 - The three data streams (standard input, standard output, and standard error)
03:06 - Example of Standard Error (stderr)
03:47 - Using the echo command to find the return code
05:54 - Example of both standard output and standard error from one command
07:47 - Splitting standard output and standard error
09:06 - Number designations for stdin, stdout, and stderr
10:24 - Sending stdout and stderr to different files*🎓 FULL LINUX COURSES FROM LEARN LINUX TV*

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I've been using linux for years and never really understood this. Thank you so much!

clblanchard

And that's why I'm proud of myself...
I never think I know everything.
I'm a linux administrator as part of my day job and I think I got a good amount of experience with the command line but reading the title of the video made me think "Maybe I'll learn something new about stdout and stderr".
I wasn't wrong.

"find /etc -type f > ~/results.txt 2> ~/errors.txt"
Never knew or thought about splitting the streams.
THANK YOU FOR THAT!
So useful.

RayBitton

When I am introducing someone to the command line this is my go to example of where the command line interface still wins out over a graphical program. The beauty is the application(s) being used don't need to be changed in any way as it is the shell that handles it all for you (providing the applications output to stdout and stderr properly).

I once worked with someone that was very "ugh I hate the command line, it's not the 1980s anymore, GUI is always better" so I asked then to do just what you did. Output valid results to one file and errors to another. The only way he could do it was manually and by actually looking then copy/paste the errors to a separate file as none of his graphical tools could filter output (they would just save everything to a single file) so would require the application itself be updated to include such functionality.

It didn't totally win him over but it at least shut him up as he knew I would always bring that example up if he ever went on a "GUI is better" rant again 😂Truth is you use the right tool for the job, sometimes that *is* a GUI application but sometimes it's a CLI one so knowing how to best use the tools available is important.

Great video 👍

satysin

I'm here because of the bandit7 game from OverTheWire. I never thought learning Linux would be so interesting. Great video.

FigueMonk

Very nice explanation. Thank you for your teaching method in the simplest way.

yjjjgpz

I was expecting you to talk about how to output both stdout AND stderr to a file.
For anyone wondering we do it like this: find /etc -type f > combined.txt 2>&1

greob

This was incredibly clear. Thank you for the content!

hugog.cintra

You are teaching style is amazing brother ✨✨✨ one love from Tanzania, thanks for sharing, your tutorial are highly recommended to anyone interested with learning Linux.

piusvictor