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István Lantos
István Lantos

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What are your UNIX pipeline commands that saved you from lot of coding/time?

#linux #opensource #discuss #tips

This question came to my mind last day when I wanted to free up some space on my HDDs and when it comes to what to delete (feel the pain), I wanted to know without lot of right-clicks which folders are the fattiest. As a good Windows user, I installed Total Commander, because some random Google result told me to do so.

Then I realised, heck, I have an entire UNIX environment on my PC (MSYS2), so maybe there is an utterly simple one liner command for achieve this. And guess what, it has: :)

$ du -sh * | sort -h
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Life hack, place this in your .bashrc file:

# Within the current directory, list all folders and files
# and print their size, then sort it from smallest to largest:
alias du='du -sh * | sort -h'
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What are your UNIX pipeline commands, where you can combine some program's standard output and creating something wicked simple time saver?

Top comments (42)

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val_baca profile image
Valentin Baca • • Edited

The most common pipes I use are:

grep # ALL HAIL. Should know these:
grep -F # fixed/literal mode, use to search exactly what you type, no regex
grep -i # case insensitive
grep -v # reverse, shows only lines that do NOT match
grep -w # matches on "words" only, grep -w "lag" won't match "flag"

sort # usually combine with uniq

uniq # usually combined with sort

wc -l # count lines

head -n 10 # top 10! you won't believe number 7!

tail -f # tail with follow, useful for log that are being updated, such as:

tail -f | grep -i error

cut # to only get certain columns, for example:
cut -d' ' -f12-15 # split on spaces, only show columns 12 through 15
# or use gawk when dealing with buffers
gawk '{$12,$13,$14,$15}'

Here's a real command I'm using in a demo in 5 minutes to show something that's hidden deep in our logs:

tail -f our.log | grep -w "WARNING" | grep --color=always -F "something=" | cut -d' ' -f12-15

EDIT: Unfortunately that doesn't work because of file buffering. Here's an actual working command for a log that is getting updated in live, but it does effectively the same thing:

tail -f our.log| grep --line-buffered -w "WARNING" | grep --color=always -F --line-buffered "something=" | gawk '{print $12,$13,$14,$15}'

Bonus: Here's a super evil one >:)

$ yes > /dev/null & # does nothing but waste CPU
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tuomotanskanen profile image
Tuomo Tanskanen •

sort -u to optimize sort | uniq ;)

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lilorox profile image
Pierre •

Unless you need to count the unique results: blah | sort -n | uniq -c

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gregorybodnar profile image
Greg Bodnar •

Cheers for the tip about grep options. I do a lot of grepping, but I think those options will save me heaps of time in the future.

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jorinvo profile image
jorin • • Edited

I think process substitution is incredible helpful. Took me a few years to find out about it.
A super powerful command is xargs. Also make sure to have a look at the -I and -p flags, both really powerful.
I just used these two features as part of an article I wrote,
Automate Your Mac Setup and Keep It Up to Date
Compare the output of two commands, get the result list and pass in one line to another command:

comm -13 <(sort brew.txt) <(brew leaves | sort) | xargs brew rm

And some aliases I like:

# Start a webserver, also accepts a port as optional argument
alias server='python3 -m http.server'

# Copy to clipboard on Mac or Linux
alias copy="$(which pbcopy &> /dev/null && echo pbcopy || echo 'xclip -sel clip')"

# Pipe my public key to my clipboard.
alias pubkey="more ~/.ssh/id_rsa.pub | copy && echo '=> Public key copied to pasteboard.'"

If you are curious which commands you use a lot, you can find out like this:
What Are Your Most Used Shell Commands?

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ben profile image
Ben Halpern •

Oooh I feel like this is a weakness of mine. Looking forward to the responses

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lucianoq profile image
Luciano Quercia • • Edited 
alias ctrlc='xclip -selection clipboard -i'
alias ctrlv='xclip -selection clipboard -o'

Examples:

# copy something without opening editors or showing it in terminal
cat ~/.ssh/mykey.pub | ctrlc

# paste clipboard somewhere
ctrlv >> ~/.ssh/known_hosts


ctrlv | tr '[:upper:]' '[:lower:]'
ctrlv | tr -d "\n"
ctrlv | base64 -d 
ctrlv | base64
ctrlv | md5sum

cat myfile | base64 | ctrlc
cat myfile | md5sum | ctrlc



ctrlv | base64 | ctrlc
ctrlv | base64 -d | ctrlc
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r0f1 profile image
Florian Rohrer •

The Just Commit Everything command:

alias gitasdf='git add -A && git commit -m asdf && git push'
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benjaminconnelly profile image
Benjamin Connelly • • Edited

Having a shortcut to add and commit is priceless. I use this function with a useful commit message and commit often.

$lg "My useful description"

# Lazy Git
function lg() {
    git add .
    git commit -a -m "$1"
    git push
}
# End Lazy Git
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tasmo profile image
Tasmo •

This might be very dangerous if you don't git pull after your commit. So I suggest:

# Lazy Git
function lg() {
    git add .
    git commit -a -m "$1"
    git pull
    git push
}
# End Lazy Git
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benjaminconnelly profile image
Benjamin Connelly •

Thank you! I have updated my function.

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djviolin profile image
István Lantos •

I have something similar, but I'm inserting a timestamp as a commit message. Still totally useless. :)

I also replaced origin word in the git repo creation at git remote add gitlab .... So if I pushing something to gitlab, I use the gitlab command, which using git push -u gitlab --all. I have similar to Github.

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msoedov profile image
Alex Miasoiedov •

Why do you use git? Just use dropbox

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dvdmuckle profile image
David Muckle • • Edited

xargs is amazing for just about anything that doesn't like piped results. Want to pull a bunch of Docker images in one command? 

echo "ubuntu gcc alpine nginx" | xargs -n 1 docker pull
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bertvv profile image
Bert Van Vreckem •

So if I understand correctly, this is equivalent to the following?

for img in ubuntu gcc alpine nginx; do docker pull "${img}"; done

I never thought of using xargs this way, good to know!

I guess you could parallellize the loop by adding -P 0 to the xargs invocation.

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dvdmuckle profile image
David Muckle • • Edited

I didn't consider using parallelization, that's a great idea! Though, what happens with Docker if it pulls in two copies of the same image at once? If two images have the same dependency, will Docker deal with this parallel pull fine, or will it bork?

EDIT: Docker seems to handle this rather well; It just queues up the layer pulls in some arbitrary order. Still, I don't know if I entirely trust this, but I can't see a reason for this to not work (And I can see a reason that one might want this to work!).

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djviolin profile image
István Lantos •

This is cool! I never thought about that.

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erikdstock profile image
Erik •

Some dumb and possibly dangerous variations I use:

# A blunt tool to fix changed ruby files before a commit
alias precommitfix="git status -s | awk '{print $2}' | grep .rb$ | xargs bundle exec rubocop -a"

# Delete merged remote branches (remove --dry-run after verifying)
git branch -r --merged | \
grep origin | \
grep -v '>' | \
grep -v master | \
xargs -L1 | \
awk '{sub(/origin\//,"");print}'| \
xargs git push origin --delete --dry-run
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barjo profile image
Jonathan Bardin •

I often use this one get the pid of the parents of zombie process.

ps -A -ostat,ppid | awk '/[zZ]/{print $2}'

Apart from that I often use grep, sort -u, sed.

A funny one is to pipe fortune with cowsay

fortune -a | cowsay -f vader
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jonasbn profile image
Jonas Brømsø •

I have used perl in pipes a lot for when you need to change something easily using a regular expression.

$ find . -name "*Relevant*.pm" | xargs perl -pi -e 's/something/somethingelse/'

The find name part can be tweaked to suit your needs and the regular expression in the Perl part also.

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clawfire profile image
Thibault Milan •

I know it's about pipe commande but since I saw some other interesting elements without pipe in it, I want to share some of them that help me daily. Hope you don't mind.

I have multiple aliases in my .aliases but some also in my .gitconfig more specific to git.
My favorite one is : 

[alias]
        # Remove branches that have already been merged with master
    # a.k.a. ‘delete merged’
    dm = "!git branch --merged | grep -v '\\*' | xargs -n 1 git branch -d"
        # List contributors with number of commits
    contributors = shortlog --summary --numbered
        # pull repository, rebasing, by auto stashing before and restore after and prune"
        up = "pull --rebase --autostash --prune"

You can find more of them into my .dotfiles repo on github

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