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Generate random valid mac addresses
Ruby version. Also, a perl version: $perl -e 'printf("%.2x.",rand(255))for(1..5);printf("%.2x\n",rand(255))'

convert wmv into xvid avi format

geoip information
That makes a function you can put in your ~/.bashrc to run it when you need in any term with an IP as argument

Stream YouTube URL directly to mplayer.
This is the result of a several week venture without X. I found myself totally happy without X (and by extension without flash) and was able to do just about anything but watch YouTube videos... so this a the solution I came up with for that. I am sure this can be done better but this does indeed work... and tends to work far better than YouTube's ghetto proprietary flash player ;-) Replace $i with any YouTube ID you want and this will scrape the site for the _real_ URL to the full quality .FLV file on Youtube's server and will then will hand that over to mplayer (or vlc or whatever you want) to be streamed. In some browsers you can replace $i with just a % or put this in a shell script so all YouTube IDs can be handed directly off to your media player of choice for true streaming without the need for Flash or a downloader like clive. (I do however fully recommend clive if you wish to archive videos instead of streaming them) If any interest is shown I would be more than happy to provide similar commands for other sites. Most streaming flash players use similar logic to YouTube. Edit: 05/03/2011 - Updated line to work with current YouTube. It could be a lot prettier but I will probably follow up with another update when I figure out how to get rid of that pesky Grep. Sed should take that syntax... but it doesn't. Original (no longer working) command: mplayer -fs $(echo "http://youtube.com/get_video.php?$(curl -s $youtube_url | sed -n "/watch_fullscreen/s;.*\(video_id.\+\)&title.*;\1;p")")

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Get the full path of a bash script's Git repository head.
Rather than complicated and fragile paths relative to a script like "../../other", this command will retrieve the full path of the file's repository head. Safe with spaces in directory names. Works within a symlinked directory. Broken down: $cd "$(dirname "${BASH_SOURCE[0]}")" temporarily changes directories within this expansion. Double quoted "$(dirname" and ")" with unquoted ${BASH_SOURCE[0]} allows spaces in the path. $git rev-parse --show-toplevel gets the full path of the repository head of the current working directory, which was temporarily changed by the "cd".

This allows you to find a string on a set of files recursivly
The -r is for recursive, -F for fixed strings, --include='*.txt' identifies you want all txt files to be search any wildcard will apply, then the string you are looking for and the final * to ensure you go through all files and folders within the folder you execute it.

repeat a command every one second
Short method of "while x=0; do foo ; sleep 1 ; done"

Speed up launch of liferea
If you use liferea frequently, you will see obvious speedup after you executed this command.

Rename files in batch


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