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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"

Windows telnet
Check if TCP port is reacheable

Kill XMMS for a cron job

find and reduce 8x parallel the size of PNG images without loosing quality via optipng

Avoid killing the X server with CTRL+C on the tty it was started from

Create QR codes from a URL.
QR codes are those funny square 2d bar codes that everyone seems to be pointing their smart phones at. Try the following... $ qrurl http://xkcd.com Then open qr.*.png in your favorite image viewer. Point your the bar code reader on your smart phone at the code, and you'll shortly be reading xkcd on your phone. URLs are not the only thing that can be encoded by QR codes... short texts (to around 2K) can be encoded this way, although this function doesn't do any URL encoding, so unless you want to do that by hand it won't be useful for that.

Get your external IP address ( 10 characters long )
Shortest url to a external IP-service, 10 characters.

vi keybindings with info
Info has some of the worst keybindings I've ever seen. Being a vim user, I attribute that to emacs influence. Use the --vi-keys option to use some of the vi keybindings, although this won't change all the keybindings. Use the "infokey" program to have more control over info keybindings.

using scanner device from command line
you have to replace "mustek_usb" with the scanner found by `scanimage -l`

Convert DOS newlines (CR/LF) to Unix format
Convert DOS newlines (CR/LF) to Unix format using sed command


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