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.

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:



2011-03-12 - Confoo 2011 presentation
Slides are available from the commandlinefu presentation at Confoo 2011: http://presentations.codeinthehole.com/confoo2011/
2011-01-04 - Moderation now required for new commands
To try and put and end to the spamming, new commands require moderation before they will appear on the site.
2010-12-27 - Apologies for not banning the trolls sooner
Have been away from the interwebs over Christmas. Will be more vigilant henceforth.
2010-09-24 - OAuth and pagination problems fixed
Apologies for the delay in getting Twitter's OAuth supported. Annoying pagination gremlin also fixed.

Top Tags



Unique number by Mac Address

Terminal - Unique number by Mac Address
UNIQUE_BY_MAC=$(ifconfig |grep eth0|awk '{ print strtonum("0x"substr($6,16,2)) }')
2010-06-01 17:34:43
User: rubo77
Functions: awk grep ifconfig
Unique number by Mac Address

gets the last number of the mac address to use it for other stuff


There is 1 alternative - vote for the best!

Terminal - Alternatives

Know a better way?

If you can do better, submit your command here.

What others think

5 not $6. if $6 for you then it means that your command don't work on some distribs according probably to ifconfig version.
Comment by pepin 252 weeks ago

Not random at all. It would be more suitable to call it a non-unique hardware ID. Consider using

printf '%x' "$((RANDOM % 256))"


Comment by bugmenot 251 weeks and 6 days ago

What's more I've hot en0 and en1 on a Mac and not eth0.

Comment by bugmenot 251 weeks and 6 days ago


i changed it to $5 and call it unique instead of "random"

Comment by rubo77 231 weeks and 6 days ago

no, if i change it to $5 it doesent work on ubuntu (debian)!

the idea is for example to get the


out of

eth0 Link encap:Ethernet Hardware Adresse 00:12:b7:88:1c:f3

and change that to an integer, which will be


in this case

sure if it doesent work on your system cause the output of ifconfig is diffenren t try with $5:

UNIQUE_BY_MAC=$(ifconfig |grep eth0|awk '{ print strtonum("0x"substr($5,16,2)) }')
Comment by rubo77 231 weeks and 6 days ago

you need


installed to run awk with the strtonum() function:

sudo aptitude install gawk
Comment by rubo77 231 weeks and 6 days ago

Your point of view

You must be signed in to comment.