Hide

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again.

Delete that bloated snippets file you've been using and share your personal repository with the world. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.


If you have a new feature suggestion or find a bug, please get in touch via http://commandlinefu.uservoice.com/

Get involved!

You can sign-in using OpenID credentials, or register a traditional username and password.

First-time OpenID users will be automatically assigned a username which can be changed after signing in.

Universal configuration monitoring and system of record for IT.
Hide

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for:

Hide

News

May 19, 2015 - A Look At The New Commandlinefu
I've put together a short writeup on what kind of newness you can expect from the next iteration of clfu. Check it out here.
March 2, 2015 - New Management
I'm Jon, I'll be maintaining and improving clfu. Thanks to David for building such a great resource!
Hide

Top Tags

Hide

Functions

Hide

Credits

Pick a random line from a file

Terminal - Pick a random line from a file
sort -R file.txt | head -1
2009-07-23 22:24:52
User: dfego
Functions: head sort
2
Pick a random line from a file

Alternatives

There are 2 alternatives - vote for the best!

Terminal - Alternatives
shuf -n1 file.txt
perl -e 'rand($.) < 1 && ($line = $_) while <>;'
2011-04-25 21:28:26
Functions: perl
Tags: perl knuth
1

This is from perldoc -q random.*line, which says:

This has a significant advantage in space over reading the whole file in. You can find a proof of this method in The Art of Computer Programming, Volume 2, Section 3.4.2, by Donald E. Knuth.

Who am I to argue with Don Knuth?

head -$(($RANDOM % $(wc -l < file.txt) +1 )) file.txt | tail -1
2009-07-23 12:00:49
User: sharfah
Functions: head tail wc
-4

prints a random line

shuf file.txt | head -n 1

Know a better way?

If you can do better, submit your command here.

What others think

excellent. i wish -R was a standard option though :(

Comment by recursiverse 318 weeks and 6 days ago
rl -c 1

(rl stands for "Randomize Lines" and can be easily installed on most distribs when not already done)

Comment by Josay 318 weeks and 6 days ago

rl is available as package 'randomize-lines' under debian/ubuntu.

Comment by bwoodacre 318 weeks and 6 days ago

shuf -n1 file.txt

Comment by sklm 318 weeks and 6 days ago

even better! shuf is part of GNU coreutils.

Comment by bwoodacre 318 weeks and 6 days ago

The third one is the only one that doesn't require GNU coreutils.

Comment by andrew112358 318 weeks and 5 days ago

Your point of view

You must be signed in to comment.