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Write comments to your history.
A null operation with the name 'comment', allowing comments to be written to HISTFILE. Prepending '#' to a command will *not* write the command to the history file, although it will be available for the current session, thus '#' is not useful for keeping track of comments past the current session.

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"

View the current number of free/used inodes in a file system
tune2fs also provides the same information . But the information does not give the current usage , it gives the information when the file system was last mounted. http://www.zaman4linux.in/2010/10/using-up-all-the-free-inodes.html

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

Hear the mice moving
Beeps on mouse's every move. Bear in mind that, at least on Ubuntu, /dev/input/mice can be read only by root.

Convert a Nero Image File to ISO
This line removes the 300k header from a Nero image file converting it to ISO format

ascii digital clock
# ### ### # # ### ### # # # ## # # ### # # # # ### ## # # # # # # ### # # # # ### # # # # # ### ##### # # ##### # # # ### # # ### # # # # # ### # # ### # # ##### ### ### # ##### ### ##### #

Find the package that installed a command

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.

Get video information with ffmpeg
I used an flv in my example, but it'll work on any file ffmpeg supports. It says it wants an output file, but it tells what you want to know without one.


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