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



view the system memory in clear text

Terminal - view the system memory in clear text
hexdump -e '90/1 "%_p" "\n"' /dev/mem | less
2009-05-12 16:20:57
User: copremesis
Functions: hexdump
view the system memory in clear text

see what's in your memory right now... sometimes you find passwords, account numbers and url's that were recently used. Anyone have a safe command to clear the memory without rebooting?


There are 2 alternatives - vote for the best!

Terminal - Alternatives

Know a better way?

If you can do better, submit your command here.

What others think

Of course access to /dev/mem depends on being root or being in the 'kmem' group (on my ubuntu system). But then when accessing memory raw like that as a user, you have no idea whether a particular physical address is currently in use because you do not have access to the kernel's data structures (even as root) if you're thinking of writing to that memory for the purposes of 'clearing' it. At least that's my understanding.

This memory scrubbing is probably best done at the application level, and many applications where security matters a bit more do take steps to clear memory areas before freeing them.

Also, rebooting doesn't necessarily clear the contents of memory: http://en.wikipedia.org/wiki/Cold_boot_attack

Comment by bwoodacre 309 weeks and 3 days ago

/dev/mem should already be restricted to only root or the wheel group ... and if someone untrusted already has root access, you have worse things to worry about than someone sifting through active memory.

Comment by Mozai 175 weeks and 4 days ago

It's unnecessary for reasons as noted above and you can't and obviously shouldn't go mucking about in addresses that are allocated for shared or running programs.

But.. for the sake of argument, or if you are just super paranoid, this task is as simple as allocating memory. You can write a simple c/c++ program to call malloc() to allocate a large bit of memory and initialize it with 0's or garbage data then terminate.

Comment by egreSS 74 weeks and 5 days ago

Your point of view

You must be signed in to comment.