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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"

connect via ssh using mac address
Connect to a machine running ssh using mac address by using the "arp" command

generate random password
-B flag = don't include characters that can be confused for other characters (this helps when you give someone their password for the first time so they don't cause a lockout with, for example, denyhosts or fail2ban) -s flag = make a "secure", or hard-to-crack password -y flag = include special characters (not used in the example because so many people hate it -- however I recommend it) "1 10" = output 1 password, make it 10 characters in length For even more secure passwords please use the -y flag to include special characters like so: $ pwgen -Bsy 10 1 output>> }&^Y?.>7Wu

Smart renaming
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.

ruby one-liner to get the current week number

A function to output a man page as a pdf file
Tested on Fedora 12. This function will take a man page and convert it to pdf, saving the output to the current working directory. In Gnome, you can then view the output with "gnome-open file.pdf", or your favorite pdf viewer.

Create a transition between two videos
We take the first 50 frames of a.mp4 for track a, and 24 blank frames followed by b.mp4 for track b. We then create a transition from track a to track b starting from frame 25 and ending at frame 49. The output is stored in out.mp4 To view the results without saving remove "-consumer avformat:out.mp4" from the end. Documentation of the mlt framework and the melt command can be found here: http://www.mltframework.org/bin/view/MLT/Documentation

Prints new content of files
Useful to e.g. keep an eye on several logfiles.

Get absolut path to your bash-script
Another way of doing it that's a bit clearer. I'm a fan of readable code.

Delete line number 10 from file
Very useful when the ssh key of a host has changed and ssh refuses to connect to the machine, while giving you the line number that has changed in ~/.ssh/known_hosts.


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