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Print the IPv4 address of a given interface

list files recursively by size

bulk rename files with sed, one-liner
Far from my favorite, but works in sh and with an old sed that doesn't support '-E'

Turn shell tracing and verbosity (set -xv) on/off with 1 command!
Running this command turns shell tracing and shell verbose debugging on or off. Not only does it do that, it also uses your terminals builtin method of setting colors to make debugging much easier. It looks at the current shell options contained in the $- special bash variable and that lets this function set the opposite of the current value. So from the shell you could do a: $ setx; echo "y" | ( cat -t ) | echo "d"; setx and it will turn on debbuggin. This is an amazingly useful function that is perfect to add system-wide by adding it to /etc/profile or /etc/bashrc.. You can run it from the shell, and you can also use it in your shell scripts like my .bash_profile - http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html

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" }

Multi-segment file downloading with lftp
This is for files only, for directories 'mirror' has to be used.

last.fm rss parser
you can just use one awk script to parse the rss feed. No need to pipe so many awk's and sed's. Its ugly and inefficient.

Tweak system files without invoking a root shell
only for sudo-style systems. Use this construct instead of I/O re-directors ``>'' or ``>>'' because sudo only elevates the commands and *not* the re-directors. ***warning: remember that the `tee` command will clobber file contents unless it is given the ``-a'' argument Also, for extra security, the "left" command is still run unprivileged.

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"

Copy from host 1 to host 2 through your host


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