Commands using xargs (769)

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Recursively execute command on directories (.svn, permissions, etc)
The above command will set the GID bit on all directories named .svn in the current directory recursively. This makes the group ownership of all .svn folders be the group ownership for all files created in that folder, no matter the user. This is useful for me as the subversion working directory on my server is also the live website and needs to be auto committed to subversion every so often via cron as well as worked on by multiple users. Setting the GID bit on the .svn folders makes sure we don't have a mix of .svn metadata created by a slew of different users.

Reducing image size
Adding the exclamation mark to the image geometry ignores the original aspect ratio. More info about image geometry: http://www.imagemagick.org/script/command-line-processing.php#geometry

Drop or block attackers IP with null routes
Someone might attack on your system. You can drop attacker IP using IPtables. However, you can use route command to null route unwanted traffic. A null route (also called as blackhole route) is a network route or kernel routing table entry that goes nowhere. Matching packets are dropped (ignored) rather than forwarded, acting as a kind of very limited firewall. The act of using null routes is often called blackhole filtering.

Display the output of a command from the first line until the first instance of a regular expression.
Slightly simpler version of previous sed command that does the same thing. In this case, the output will stop at the command, and the entire command will be terminated as well, instead of proceeding through the whole file.

List the binaries installed by a Debian package
This shell function displays a list of binaries contained in an installed package; works on Debian based Linux distributions.

Doing some floating point calculations with rounding (e.g. at the 3rd decimal)

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Change size of lots of image files.
Imagemagick library is used.

Get your external IP address with a random commandlinefu.com command
There's been so many ways submitted to get your external IP address that I decided we all need a command that will just go pick a random one from the list and run it. This gets a list of "Get your external IP" commands from commanlinefu.com and selects a random one to run. It will run the command and print out which command it used. This is not a serious entry, but it was a learning exercise for me writing it. My personal favourite is "curl icanhazip.com". I really don't think we need any other ways to do this, but if more come you can make use of them with this command ;o). Here's a more useful command that always gets the top voted "External IP" command, but it's not so much fun: $ eval $(curl -s http://www.commandlinefu.com/commands/matching/external/ZXh0ZXJuYWw=/sort-by-votes/plaintext|sed -n '/^# Get your external IP address$/{n;p;q}')


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