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.

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.

UpGuard checks and validates configurations for every major OS, network device, and cloud provider.

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:



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!

Top Tags



Filter IPs out of files

Terminal - Filter IPs out of files
egrep -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' file.txt
2009-05-28 14:46:17
User: P17
Functions: egrep
Filter IPs out of files

Know a better way?

If you can do better, submit your command here.

What others think

egrep -wo '([0-9]{1,3}\.){3}[0-9]{1,3}' file.txt

selects on word boundaries and is slightly less verbose

Comment by kiwi 459 weeks and 2 days ago

cool didn't know about the -o option ....

Comment by copremesis 459 weeks and 2 days ago

perl version:

perl -ne's/(\d{1,3}\.){3}\d{1,3}/print"$&\n"/ge' file.txt

and, perl version (word boundary):

perl -ne's/\b(\d{1,3}\.){3}\d{1,3}\b/print"$&\n"/ge' file.txt

Comment by wbx 459 weeks and 2 days ago

This is all *plain wrong*, you extract 4 numbers (Each up to three digits) seperated by dots with these regexes. These numbers don't have to be valid IPs.


echo "999.999.999.999" > file.txt echo "" >> file.txt perl -ne's/(\d{1,3}\.){3}\d{1,3}/print"$&\n"/ge' file.txt


egrep -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' file.txt


Better use sth. like that (Not mine, found with google):

egrep '\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b' file.txt

Comment by OJM 459 weeks and 1 day ago

Your point of view

You must be signed in to comment.