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.

Universal configuration monitoring and system of record for IT.

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



Psst. Open beta.

Wow, didn't really expect you to read this far down. The latest iteration of the site is in open beta. It's a gentle open beta-- not in prime-time just yet. It's being hosted over at UpGuard (link) and you are more than welcome to give it a shot. Couple things:

  • » The open beta is running a copy of the database that will not carry over to the final version. Don't post anything you don't mind losing.
  • » If you wish to use your user account, you will probably need to reset your password.
Your feedback is appreciated via the form on the beta page. Thanks! -Jon & CLFU Team

Match non-empty lines

Terminal - Match non-empty lines
grep -v "^\W$" <filename>
2009-06-18 08:17:22
User: nikc
Functions: grep
Match non-empty lines

I had some trouble removing empty lines from a file (perhaps due to utf-8, as it's the source of all evil), \W did the trick eventually.


There are 4 alternatives - vote for the best!

Terminal - Alternatives

Know a better way?

If you can do better, submit your command here.

What others think

I'm not sure I understand this. \W matches a single non-alphanumeric character. The -v option negates the match. So your command prints all lines that do not consist of a single non-alphanumeric character. Maybe it was a line with MS-DOS line endings, i.e. CR-LF sequences, so the "empty" lines actually contained a single CR character? (Remember that UNIX only considers LF to terminate lines.)

Anyway, there are several simple ways to print all non-empty lines (provided you have a UNIX text file with LF line termination). The simplest one is this:

grep . file.txt

But these work, too:

grep -vx "" file.txt awk /./ file.txt sed -n /./p file.txt sed '/^$/d' file.txt tr -s \\n < file.txt echo g/./p | ed -s file.txt

... and many more.

Comment by inof 410 weeks and 1 day ago

My preferred way:

grep -v "^$" file.txt
Comment by unixmonkey3280 410 weeks ago

Your point of view

You must be signed in to comment.