Which Linux command or utility is simple, powerful, and surprisingly unknown to many people or used less often?
This could be a command or a piece of software or an application.
For example I’m surprised to find that many people are unaware of Caddy, a very simple web server that can make setting up a reverse proxy incredibly easy.
Another example is fzf. Many people overlook this, a fast command-line fuzzy finder. It’s versatile for searching files, directories, or even shell history with minimal effort.
socat- connect anything to anythingfor example
socat - tcp-connect:remote-server:12345socat tcp-listen:12345 -socat tcp-listen:12345 tcp-connect:remote-server:12345Pandoc.
Converts any rich text format to any other.
Not powerful, but often useful,
column -taligns columns in all lines. EG$ echo {a,bb,ccc}{5,10,9999,888} | xargs -n3 a5 a10 a9999 a888 bb5 bb10 bb9999 bb888 ccc5 ccc10 ccc9999 ccc888 $ echo {a,bb,ccc}{5,10,9999,888} | xargs -n3 | column -t a5 a10 a9999 a888 bb5 bb10 bb9999 bb888 ccc5 ccc10 ccc9999 ccc888wait, shell could make matrix multiplication ?
No, that’s just brace expansion.
netstat -tunlshows all open ports on the machine to help diagnose any firewall issues.netstat is kind of deprecated,
ssis more modern (from the iproute2 package) and uses very similar parameters.
nmap *your_local_ip_address*for example
nmap 192.168.1.43/24will show you what devices are connected to the local network, and what ports are open there. really useful, for example, when you forgot the address of your printer or raspi yet again.you can also use it to understand what ports on your computer are open from an attacker’s perspective, or simply to figure out what services are running (ssh service).
losetupit’s useful for dealing with virtual disk images. like a real physical hard disk, but it’s a file on the computer. you can mount it, format it, and write it to a real physical disk.
it’s sometimes used with virtual machines, with iso images, or when preparing a bootable disk.
Control+r == search through your bash history.
I used linux for ten years before finding out about that one.
Works much better with fzf, but even just default bash it’s useful.
i just cat grep .bash_history lol
but this does sound more convenient xD
Man not even using the history command
well if it makes you feel better you just made me
man historyxD
Man
dude
Bruh
probably well known at this point but rsync is incredible and I use it all the time
bcIt’s a simple command line calculator! I use it all the time.
Very useful for shell scripts that need to do maths as well. I use it to make percentages when stdout has values between 0.0 and 1.0
jq - super powerful json parser. Useful by hand and in scripts
I love jq, but I wouldn’t call it “surprising simple” for anything but pretty-formatting json. It has a fairly steep learning curve for doing anything with all but the simplest operations on the simplest data structures.
xargs
Very true. I used to do magic with xargs when working as a sysadm. Also a good way to mess up on a grand scale. Ask me how I know.
So, how do you know?
By not testing it properly before running it over the whole file system resulting in a few hours of extra work cleaning up the mess I made.
batcat
It’s like cat but better. Great for when you just want to look at the contents of a file, without loading a whole text editor.
Oh also, tldr
My procedure for learning how to use a cli command goes tldr page -> --help if the tldr fails to help me -> THEN the full manpage
I like batcat aka bat, but nominate the humble ‘cat’ instead.
Want to copy a disk image to a device? You can use cat for that:
cat file.iso>/dev/sdfWhat to copy local stdout over ssh? Use cat.
ls -l | ssh myhost 'cat >out.txt'That’s simple and surprisingly powerful.
ip eg:
# ip a # ip a a 192.168.1.99/24 dev enp160The first incantation - ip address (you can abbreviate whilst it is unambiguous) gets you a quick report of interfaces, MAC, IPs and so on. The second command assigns another IP address to an interface. Handy for setting up devices which don’t do DHCP out of the box or already have an IP and need a good talking to.
Oh and you can completely set up your IP stack, interfaces and routing etc with it. Throw in nft or iptables (old school these days - sigh!) for filtering and other network packet mangling shenanigans.
yesThe most positive command you’ll ever use.
Run it normally and it just spams ‘y’ from the keyboard. But when one of the commands above is piped to it, then it will respond with ‘y’. Not every command has a true -y to automate acceptance of prompts and that’s what this is for.
Also, you can make
yesreturn anything:yes noI… did not know that. Thanks, TIL!
That’s really neat but also seems like it could be quite dangerous in a lot of use-cases!
Absolutely, but when you do need it, it’s brilliant.
What’s the syntax here? Do I go
command && yes
I’m not sure if I’ve had a use case for it, but it’s interesting.
Also my favourite way to push a core to 100% CPU
yes > /dev/nullhow is that better than
cat /dev/zero > /dev/nullor
while true; do :; doneWho said it was better? It’s just my favourite.
Like my favourite shirt, it’s no better than the others, but it brings me a little joy :)
- on a serious note though, thank you for sharing your two examples - I didn’t know they existed.
That will just wait for
commandto finish properly and then runyes.What you want to run is
yes | command, so it spams the command with confirmations.Sorry, I should have explained that. it’s
command | yesyes|command- Eg,yes|apt-get update(Not a great example since apt-get has -y, but sometimes that fails when prompting for new keys to accept)Edit: I got it backwards, thanks @[email protected] for the correction.
You’ve got it backwards - you need to pipe the output of
yesinto the input of the command:yes | command-that-asks-a-lot-of-questionsSo I did - thanks for the correction, edited.
truedelivers error level 0,falseerror level 1.yes && echo True || echo Falsewill always be True.false && echo True || echo Falsewill always be False.Common usage is for tools that ask for permissions and similiar.
yes | cp -ihas the same effect ascp --force(-i: prompt before overwrites).For some cases I use “|| true”.
The idiom accepts that the preceding command might fail, and that’s OK.
For example, a script where mkdir creates a directory that might already exist.
mkdir -pwill not complain if the dir existsRight, it was an example of a pattern. In that case, -p could be used.
I figured as much. Just wanted to show another option.
