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Grab a list of MP3s out of Firefox's cache
Ever gone to a site that has an MP3 embedded into a pesky flash player, but no download link? Well, this one-liner will yank the names of those tunes straight out of FF's cache in a nice, easy to read list. What you do with them after that is *ahem* no concern of mine. ;)

Set laptop display brightness
Run as root. Path may vary depending on laptop model and video card (this was tested on an Acer laptop with ATI HD3200 video). $ cat /proc/acpi/video/VGA/LCD/brightness to discover the possible values for your display.

Mirror a directory structure from websites with an Apache-generated file indexes
wget/curl/friends are not good with mirroring files off websites, especially those with Apache-generated directory listings. These tools endlessly waste time downloading useless index HTML pages. lftp's mirror command does a better job without the mess.

Use AWS CLI and JQ to get a list of instances sorted by launch time
Use the AWS CLI tools to generate a list instances, then pipe them to JQ to show only their launch time and instance id. Finally use sort to bring them out in runtime order. Find all those instances you launched months ago and have forgotten about.

Define shell variable HISTIGNORE so that comments (lines starting with #) appear in shell history
I was surprised to find that with RedHat bash, I could not find any comment lines (begining with #) in my bash shell history. Surprised because in Mageia Linux this works. It turns out that RedHat's bash will keep comment lines if in my .bashrc, I define: export HISTIGNORE=' cd "`*: PROMPT_COMMAND=?*?' Why have comment lines in shell history? It's a handy and convenient way to make proto-commands (to be completed later) and for storing brief text data that is searchable in shell history.

On Screen micro display for battery and CPU temperature. nifty, small, omnipresent
My firefox overheats my cpu, sometimes above 90 degrees Celsius ( hence the name? ) To keep an eye on temperature, I put this command inside KAlarm ( a kind of cron) to be repeated every minute, for 5 seconds, color red ( default for osd_cat). Its pretty, ultra small, displays a micro 2 lines text on every desktop and over everything and do not steal focus or interrupt any task. I get the information passively, in the low profile bottom of the screen. Of course you can use it inside a terminal. Just do it: watch -n 60 'acpi -t | osd_cat -p bottom'

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" }

print contents of file from line 1 until we match regex
Start printing the contents of filename to stdout, until a matching line to regex is found, then stop.

Single words from Amazon Kindle 3 notes
You can use any dictionary you want, in any language. This command will output all single-word annotations that you have underlined in your Kindle device (provided the file) given a list of language-specific words. If you want to learn vocabulary, this command is ideal.

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" }


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