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Awk: Perform a rolling average on a column of data
Sometimes jittery data hides trends, performing a rolling average can give a clearer view.

Get list of servers with a specific port open
Change the -p argument for the port number. See "man nmap" for different ways to specify address ranges.

Record microphone input and output to date stamped mp3 file
record audio notes or meetings requires arecord and lame run mp3gain on the resulting file to increase the volume / quality ctrl-c to stop recording

create disk copy over the net without temp files
I wanted to create a copy of my whole laptop disk on an lvm disk of the same size. First I created the logical volume: lvcreate -L120G -nlaptop mylvms SOURCE: dd if=/dev/sda bs=16065b | netcat ip-target 1234 TARGET: nc -l -p 1234 | dd of=/dev/mapper/mylvms-laptop bs=16065b to follow its process you issue the following command in a different terminal STATS: on target in a different terminal: watch -n60 -- kill -USR1 $(pgrep dd) (see http://www.commandlinefu.com/commands/view/4356/output-stats-from-a-running-dd-command-to-see-its-progress)

Write on the console without being registered
just use a space to prevent commands from being recorded in bash's history on most systems

Prefix every line with a timestamp

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" }

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.

A snooze button for xmms2 alarm clock
you can also run "xmms2 pause & at now +5min

Current running process ordered by %CPU
Useful to detect which process is causing system loads. It shows process PID so as we can take further actions.


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