What I've Learned This Week

I’ve been homelabbing for a few years now, and recently I’ve really been focusing in on learning how to use gnu/linux. I thought it might be fun to periodically share the things I’ve been learning. The stand outs for me this past week were:

  1. Use the full path when referencing files and directories in bash scripts (Edit: when it makes sense, which is something I’m also still learning. This mkaes sense when the files will always be located in the same place.)
  2. In a bash script, the variable ${file##*/} will get you the name of the file your script is handling (example, when looping over files in a directory. I believe that’s a shell/bash standard variable, but I need to learn where it came from and how it works)
  3. Ubuntu gets a ton of justifiable criticism, but I find Canonical’s Multipass to be a great tool for spinning up Linux virtual machines. Especially on Apple silicon macs.
  4. Piping the output of ls to grep as a variable in a path is a great way to change to a directory you know exists but can’t remember the exact name of. (Example: cd ~/movies/“$(ls ~/movies | grep movie-name)”)
  5. The reason Mac cli utilities have syntax variations compared to the standard gnu/linux utilities is because macOS and its cli utilities are BSD based. This was information I knew at a high level, but had never really understood the implications of until this week.
  6. Related to point 5, if you’re on macOS trying to learn and you’re annoyed by the syntax differences between bsd and gnu utilities, you can run this script from darksonic37 on github to remove the bsd utilities from macOS and replace them with their gnu counterparts. (I have not run or reviewed the script. I found mulitpass first, and so far I’m happy using the Ubuntu virtual machine)
ABeeinSpace, (edited )

This is really great info! I never knew Multipass existed, thanks for sharing.

For macOS, Homebrew can be used to selectively replace certain parts of the coreutils with the GNU versions

Edit: On reviewing the script you mentioned, that’s exactly what it does. It uses Homebrew to replace all the coreutils in one go

harsh3466,

You’re welcome! I stumbled across Multipass when I was looking for virtual machine options for the m1 mac mini I’m working on. I specifically was trying to get away from using the mac coreutils for a consistent syntax experience, and Multipass has been working perfectly for that.

It was only after I’d been using Multipass already that I stumbled across that script, and planned to take a look at it to possibly implement on my machine. I didn’t realize that Homebrew allowed for replacing the coreutils with the GNU versions. Another thing learned!

genie, (edited )

Thanks for putting this out for public benefit! I haven’t messed around with MacOS much but the things you’ve mentioned are nice to know.

I believe that’s a shell/bash standard variable, but I need to learn where it came from and how it works

You may know this already, but I’ve found the man (as in manual) utility to be one of the most useful things in GNU/Linux user space. I don’t have much insight into ‘${file##*/}’ off the cuff, but I can tell you there’s manual entries for file, sh, and bash that may help you track it down.


<span style="font-style:italic;color:#969896;"># simply type man [some-command]
</span><span style="color:#323232;">man file
</span><span style="color:#323232;">man sh
</span><span style="color:#323232;">man bash
</span><span style="color:#323232;">man man </span><span style="font-style:italic;color:#969896;"># very useful for getting started!
</span>

Manpages are local to your system so they’re extremely fast to pull up and searchable!

Here’s some online info on man if you’re interested:

(30 sec read) Unix stack exchange tips & tricks

(5 min read) It’s FOSS writeup

harsh3466,

Yes, thank you! The man pages have been a huge help as I’m working through things. Sometimes I don’t know enough to understand what the man pages are telling me, and then I usually end up on stack exchange looking at a command example that someone has helpfully broken down.

genie,

It’s definitely a skill that I haven’t mastered either! That being said I think it’s one of the pillars of being a bonafide “super user” and I’d like to set there one day :)

Maybe I’ll take inspiration from this post and write something up about what I learn in the future about manpages.

Cheers and happy tinkering!

harsh3466,

I agree, and I’d like to be there as well so that I can easily read and understand a man page.

Deckweiss, (edited )

Well, if you didn’t replace grep with gnu/grep then you should call it belllabs/gnu/linux. Oh and don’t forget canonical for consistency: canonical/belllabs/gnu/linux

Keep in mind to sort the complete list by cpu cycles used by each of the projects on your specific system in ascending order. Maybe you can write a canonical/belllabs/gnu/linux script to automatically keep track and output an up to date string for easy proper nomenclature.

/s

davidgro,

I generally agree with the message behind this sarcasm, but in this specific case OP really is learning the GNU utilities in particular (via Linux) so I don’t mind the extra nomenclature.

Deckweiss, (edited )

except for grep and multipass, which aren’t gnu, and amount to half of the utilities mentioned in the post if I read it correctly 🤷

davidgro,

You’re certainly right about Multipass, but the grep included in Ubuntu does seem to be from GNU.

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