Linux

vd (VisiData) is a wonderful TUI spreadsheet program. It can read lots of formats, like csv, sqlite, and even nested formats like json. It supports Python expressions and replayable commands.

I find it most useful for large CSV files from various sources. Logs and reports from a lot of the tools I use can easily be tens of thousands of rows, and it can take many minutes just to open them in GUI apps like Excel or LibreOffice.

I frequently need to re-export fresh data, so I find myself needing to re-process and re-arrange it every time, which visidata makes easy (well, easier) with its replayable command files. So e.g. I can write a script to open a raw csv, add a formula column, resize all columns to fit their content, set the column types as appropriate, and sort it the way I need it. So I can do direct from exporting the data to reading it with no preprocessing in between.

A really simple one but surprisingly useful is cal

Use less for checking contents of files. Many people use cat all the time, but I don't like it, because if you do that often, your terminal window quickly gets flooded with stuff, and then you have to scroll up and down if you wanna see a previous output. With less, your file opens in a different "frame", which you can close when you're done.

miniserve

A static file server, I use it for temporary file share in company, just run miniserve . in the folder.

dua

Alternative of du command, run dua i for a text UI

GNU datamash (https://www.gnu.org/software/datamash/alternatives/) - handy tool for data munching. There's also https://github.com/BurntSushi/xsv

I like https://github.com/aristocratos/btop personally. It's way prettier than the normal top command which you use to watch processes to find the one that's hogging all of the CPU or whatever. And it's not so much that it's underrated so much as it's not very well known or distributed by default.

paste. I don't think a lot of people know this command, but it can be handy at times

• awk
• the (usually rust-based) coreutils "alternatives" like bat, fd, eza, procs
• trash-put (rm with trash integration. But beware that it also operates on directories by default, which rm only does with -r. There should be an option to change that behavior but there isn't. Don't alias rm to this)
• wl-copy/paste (or the older one for X11, 'xclip' IIRC. Enables you to do stuff like "cat image.jpg | wl-copy" to copy it to the clipboard. Best alias it to something shorter)
• xdg-open (open the file using your associated program for that file type. Alias to "o" or so)
• pass (awesome password manager, when you have a GPG key pair. Even better in combination with e.g. wofi)
• notify-send (to send GUI notifications from shell scripts)
• ledger (plain-text accounting software. If you use Emacs you should take a look at this as it's written by an Emacs dev, and has good integration of course)
• nc
• nohup

awk

..for parsing the output of other commands quickly and simply. Then that parsed output can be used to create simple log messages or be passed as args to other scripts. Powerful.

I like btop Maybe not really "unknown", but hey for those that don't know about it, check it out!

Lightweight sudo alternatives, hard to google too. I know ssu and rdo, please mention others.