commandlinefu.com is the place to record those command-line gems that you return to again and again.
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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.
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,…):
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Useful for switching over someone else's coding style who uses camelCase notation to your style using all lowercase with underscores.
Clone linux installation.
Copy every file from current directory to destination preserving modification time.
From screen's manpage: "Attach here and now. In detail this means: If a session is running, then reattach. If necessary detach and logout remotely first. If it was not running create it and notify the user. This is the author's favorite."
Toss this in your ~/.bash_profile so that you never have that "oh crap" moment where you wanted to run something in screen and didn't.
GNU shred is provided by the coreutils package on most Linux distribution (meaning, you probably have it installed already), and is capable of wiping a device to DoD standards.
You can give shred any file to destroy, be it your shell history or a block device file (/dev/hdX, for IDE hard drive X, for example). Shred will overwrite the target 25 times by default, but 3 is enough to prevent most recovery, and 7 passes is enough for the US Department of Defense. Use the -n flag to specify the number of passes, and man shred for even more secure erasing fun.
Note that shredding your shell history may not be terribly effective on devices with journaling filesystems, RAID copies or snapshot copies, but if you're wiping a single disk, none of that is a concern. Also, it takes quite a while :)
Installing most OSX apps is just a matter of dropping it in /Applications, either GUI-wise or with cp -r. However, many packages are distributed in "mpkg" format, and those have to be installed with an installer. If you don't want to go to the trouble of firing up VNC to install an mpkg, you can use the "installer" command.
This will install an application from a .mpkg it to /Applications system-wide. To install a program for just one user, replace "-target /" with "-target username".
To unmount, replace "attach" with "eject"
This will, for an application that has already been removed but had its configuration left behind, purge that configuration from the system. To test it out first, you can remove the last -y, and it will show you what it will purge without actually doing it. I mean it never hurts to check first, "just in case." ;)
So you keep getting buzzes sounding from pidgin but you can't remember which buddy pounce is causing the beep. Well, cat/edit the ~/.purple/pounces and find out!
A powerfull way to rename file using sed groups.
& stand for the matched expression.
\1 referes to the first group between parenthesis. \2 to the second.
Start screen in detached mode, i.e., already running on background. The command is optional, but what is the purpose on start a blank screen process that way?
It's useful when invoking from a script (I manage to run many wget downloads in parallel, for example).
Sometimes Firefox crashes or is bad finished and the message the process is still running appear while it's not. This also works when you sharing account from a NIS server and try to open the browser on multiple computers.
Use the lshw command to display information about your video card. Give more ouput when run as root.
Purge all configuration files of removed packages
A short way to give us relevant report in a moment done about quantities on disk usage, memory and swap in our Linux Systems.
typing history it's a long way but typing only h it's my way it works in whatever distro or OSes or shells that you use, you know, only for easyness :)
Useful for removes a package and its depends, for example to remove the gnome desktop environment, also configuration files will be removed, you should be carefully and sure that you want to do this.
Displays only the VGA adapter/chipset being used for the graphics. In this case, it gave me the "M22" and "Mobility Radeon x300" that I needed to research a graphics issue I was having.
This is useful if you have need to do port forwarding and your router doesn't assign static IPs, you can add it to a script in a cron job that checks if you IP as recently changed or with a trigger script.
This was tested on Mac OSX.
Use date to find the date at other days and times.
This command list and sort files by size and in reverse order, the reverse order is very helpful when you have a very long list and wish to have the biggest files at the bottom so you don't have scrool up.
The file size info is in human readable output, so ex. 1K..234M...3G
Tested with Linux (Red Hat Enterprise Edition)
Written for linux, the real example is how to produce ascii text graphs based on a numeric value (anything where uniq -c is useful is a good candidate).
If you're a moron like me, sometimes your fingers get away from you and you, for example, enter your password when you're already authenticated to ssh-agent, sudo, etc., and your password ends up in shell history. Here's how to get it out.