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Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

Have a smile
Outputs utf-8 smileys

add static arp entry to default gateway, arp poison protection

Get information about memory modules
To take information about the characteristics of the installed memory modules.

back ssh from firewalled hosts
host B (you) redirects a modem port (62220) to his local ssh. host A is a remote machine (the ones that issues the ssh cmd). once connected port 5497 is in listening mode on host B. host B just do a ssh 127.0.0.1 -p 5497 -l user and reaches the remote host'ssh. This can be used also for vnc and so on.

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"

Use a var with more text only if it exists
See "Parameter Expansion" in the bash manpage. They refer to this as "Use Alternate Value", but we're including the var in the at alternative.

Matrix Style
Unlike other alternatives, this command only relies on bash builtins and should also work on windows platforms with the bash executable. Sparseness corresponds to the number 128 and can be adjusted. To print all possible digits instead of only 0 and 1 replace RANDOM%2 by RANDOM%10 or RANDOM%16 to add letters [A-F].

Find the package that installed a command

get the latest version
to download latest version of "util", maybe insert a sort if they wont be shown in right order. curl lists all files on mirror, grep your util, tail -1 will gets the one lists on the bottom and get it with wget


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