Linux

https://blog.sanctum.geek.nz/series/unix-as-ide/

# list all recursive files sorted by size  
$ fd -tf "" -x du -h | sort -h  
8.0K      ./asdfrc  
 20K      ./nvim/lua/lush_theme/bleak.lua  
 32K      ./alacritty.yml  

# find files by extension  
$ fd -e lua  
nvim/colors/bleak.lua  
nvim/init.lua  
nvim/lua/config/autocmds.lua  

# list found files in tree view  
$ fd -e lua | tree --fromfile  
.  
└── nvim  
    ├── colors  
    │   └── bleak.lua  
    ├── init.lua  

# Run "npm test" when a file changes in the src or test directories  
$ fd src test | entr -- npm test  

# find out how often you use each command  
history | cut -d " " -f 1 | sort | uniq -c | sort -n | tail -n 10  
  80 rm  
  81 lsd  
 107 asdf  
 136 npx  
 161 find  
 176 fd  
 182 cd  
 185 rg  
 247 brew  
 250 nb  
 465 npm  
 867 git  

Another one of my favorite is ctrl+r to quickly search for a previous command.

Then type in a word from the command you are looking for and then hit tab to find the right command if there is more than one with that word.

Something that really improved my life was learn to properly use find, grep, xargs and sed. Besides that, there are these two little 'hacks' that are really handy at times...

1- find out which process is using some local port (i.e. the modern netstat replacement):

$ ss -ltnp 'sport = :<port-number>'

2- find out which process is consuming your bandwidth:

$ sudo nethogs

ripgrep

i do not know if this counts as a command but you might want to check Atuin, what it does is help you find, manage and edit the commands you used in your shell history saves you a lot of time

docker run --rm -it --privileged --pid=host debian:12 nsenter -a -t1 "$(which bash)"

If your user is in the docker group, and you are not running rootless Docker, this command opens a bash shell as root.

How it works:

• docker run --rm -it creates a temporary container and attaches it to the running terminal
• --privileged disables some of the container's protections
• --pid=host attaches the container to the host's PID namespace, allowing it to access all running processes
• debian:12 uses the Debian 12 image
• nsenter -a -t1 enters all the namespaces of the process with PID 1, which is the host's init since we use --pid=host
• "$(which bash)" finds the path of the host's bash and runs it inside the namespaces (plain bash may not work on NixOS hosts)

I'm not much of a one-liner collector but I like this one:

vim +copen -q <(grep -r -n <search> .) 

which searches for some string and opens all instances in vim's quickfix list (and opens the quickfix window too). Navigate the list with :cn and :cn. Complex-ish edits are the obvious use case, but I use this for browsing logs too.

Neovim improves on this with nvim -q - and [q/]q, and plenty of fuzzy finder plugins can do a better version using ripgrep, but this basic one works on any system that has gnu grep and vim.

Edit:

This isn't exactly a command, but I can't imagine not knowing about this anymore:

$ man grep
/  -n       # double space before the dash!

brings you directly to the documentation of the -n option. Not the useless synopsis or any other paragraphs that mention -n in passing, but the actual doc for this option (OK, very occasionally it fails due to word wrap, but assuming the option is documented then it works 99% of the time).

I get a lot of mileage out of the line editing commands. I think they are Emacs based and optional... but like Ctrl k, Ctrl u, Ctrl a.

fzf is great for quickly finding files e.g. in large code repositories.

tcpdump can help diagnose network issues.

Bash/ZSH aliases are invaluable for commands that you run often. I use micro as my terminal editor so I have alias m for micro and sm for sudo micro. Just 2 of maybe a dozen aliases I use. Docker has quite a large list of aliases with ZSH. Super super useful. 

(Fixed the bolding issue)

From a file I keep since I started using Linux near 5 years ago:

Display the RAM usage:
watch -n 5 free -m
Useful if you open way too much stuff and/or you're running on budget processing power, and don't want your computer freezing from 3 hours.
Also useful if you use KDE's Konsole integrated into the Dolphin file manager and you must for some reason not close the Dolphin window. You'd just need to open Dolphin's integrated Konsole (F4), run the command and without closing it, press F4 again to hide the Konsole.

Terminal-based file browser that sorts by total size:
ncdu
why is the cache folder 50 GB big?

Mass-check MD5 hashes for all files in the path, including subfolders:
find -type f \( -not -name "md5sum.txt" \) -exec md5sum '{}' \; > md5sum.txt
Change md5sum (and optionally the output file's name) for your favorite/needed hash calculator command.

For mounting ISOs and similar formats:
sudo mount -o loop path/to/iso/file/YOUR_ISO_FILE.ISO /mnt/iso

And unmounting the file:
sudo umount /mnt/iso
Beware there's no N in the umount command

For creating an ISO from a mounted disc:
dd if=/dev/cdrom of=image_name.iso

And for a folder and its files and subfolders:
mkisofs -o /path/to/output/disc.iso /path/from/input/folder

Compress and split files:
7z -v100m a output_base_file.7z input_file_or_folder

Changes the capslock key into shiftlock on Linux Mint (not tested in other distros):
setxkbmap -option caps:shiftlock
Was useful when the shift key from a previous computer broke and I didn't have a spare keyboard.

If you want to run Japanese programs on Wine, you can use:
LC_ALL=ja_JP wine /path/to/the/executable.exe
There are other options but this is one that worked the better for me so I kinda forgor to take note of them.

List all files in a given path and its subfolders:
find path_to_check -type f
Tip: add > output.txt or >> output.txt if you'd rather have the list in a TXT file.

Running a program in Wine in a virtual desktop:
wine explorer /desktop=session_name,screen_size /path/to/the/executable.exe

E.g.:
wine explorer /desktop=MyDesktop,1920x1080 Game.exe

Useful if you don't want to use the whole screen, there are integration issues between Linux, Wine and the program, or the program itself has issues when alt-tabbing or similar (looking at you, 2000's Windows games)

Download package installers from with all their dependencies:
apt download package_name
Asks for sudo password even when not running as sudo. Downloaded files come with normal user permissions thankfully. Also comes with an installation script but if you want to run it offline, iirc you need to change apt install in the script for dpkg -i.

If you use a program you'd rather not connect to the internet but without killing the whole system's connection, try:
firejail --net=none the_command_you_want_to_run

Or if you want to run an appimage:
firejail --net=none --appimage the_command_you_want_to_run

If you want to make aliases (similar to commands from Windows' PATH) and your system uses bash, edit the file $HOME/.bashrc (e.g. with Nano) and make the system use the updated file by either logging out and in, or running . ~/.bashrc

Python/Pip have some nifty tools, like Cutlet (outputs Japanese text as Romaji), gogrepoc (for downloading stuff from your account using GOG's API), itch-dl (same as gogrepoc but for Itch.io), etc. If you lack the coding skills and doesn't mind using LLMs, you could even ask one to make some simpler Python scripts (key word though: simpler).

If you want to run a video whose codec isn't supported by your system (e.g. Raspberrian which only supports H.264, up to 1080p):
ffmpeg -i input_video.mkv -map 0 -c:v libx264 -preset medium -crf 23 -vf scale=1920:1080 -c:a copy -c:s copy output_video.mkv

A couple I use (concept of not exact), that I haven't seen in the thread yet:

Using grep as diff: grep -Fxnvf orig.file copy.file

Using xargs -

xargs reads items from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is /bin/echo) one or more times with any initial-arguments followed by items read from standard input.

EG: $ find ~/Pictures -name "*.png" -type f -print0 | xargs -0 tar -cvzf images.tar.gz

cd `pwd`

for when you want to stay in a dìr that gets deleted and recreated.

cat /proc/foo/exe > program
cat /proc/foo/fd/bar > file

to undelete still-running programs and files still opened in running programs

rpm-ostree status

rpm-ostree reset

rpm-ostree rebase

idk i love rpm-ostree man

I'll go with a simple one here:

CTRL+SHIFT C/V for copy paste.

Or if it has to be terminal;

kill

😊