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.

OpenID
or
Sign in Register

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

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

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.
Hide

Tags

Hide

Functions

Hide

Credits

Site by David Winterbottom (user root).

extracts 64 bytes of random digits from random lines out of /dev/random sent to stdio

Terminal - extracts 64 bytes of random digits from random lines out of /dev/random sent to stdio
cat /dev/urandom|od -t x1|awk 'NR > line { pos=int(rand()*15)+2;printf("%s",$pos);line=NR+(rand()*1000);digits = digits+2 } digits == 64 { print("\n");exit }'
2012-08-14 19:02:00
User: jetdillo
Functions: awk cat exit od
1
Up
Down
extracts 64 bytes of random digits from random lines out of /dev/random sent to stdio

Use this the next time you need to come up with a reasonably random bitstring, like for a WPA/WPA2 PSK or something. Takes a continuous stream of bytes coming from /dev/urandom, runs it through od(1), picking a random field ($0 and $1 excluded) from a random line and then prints it.

Show sample output | Add to favourites | Report as malicious

Alternatives

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

Your command can be shortened quite a bit.

First, picking random digits out of a random stream doesn't make the result any more random

(ask a mathematician for a fuller explanation).

Next, ask pass /dev/urandom to od directly:

od -t x1 /dev/urandom | ...

Finally replace awk with an incomprehensible sed :-)

od -t x1 /dev/urandom | sed '$!N;s/\n//;s/\([0-9]\{7\}\)\| //g;2q'

Which means: Join the first two lines

$!N;s/\n//

Strip out blocks of 7 digits, or single spaces

s/\([0-9]\{7\}\)\| //g

Stop processing after two lines of input:

2q
Comment by flatcap 39 weeks and 6 days ago

Your point of view

You must be signed in to comment.

Related sites and podcasts