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Quickly generate an MD5 hash for a text string using OpenSSL
Here Strings / A variant of here documents, the format is:

Conficker Detection with NMAP

Set up alarm with fade-in, for graceful awakening
There are a lot of commands, which invokes your player at specified time. But I prefer not to jump from by bed, when alarm start to play. Instead, this script increases volume of mpd over time, which much more pleasant when you just woke up :)

sort monthwise
sort command can sort month-wise (first three letters of each month). See the sample output for clarification. Sorting Stable ? NO. Take note if that matters to you. Sample output suggests that sort performs unstable sorting (see the relative order of two 'feb' entries).

delay execution of a command that needs lots of memory and CPU time until the resources are available
[ 2000 -ge "$(free -m | awk '/buffers.cache:/ {print $4}')" ] returns true if less than 2000 MB of RAM are available, so adjust this number to your needs. [ $(echo "$(uptime | awk '{print $10}' | sed -e 's/,$//' -e 's/,/./') >= $(grep -c ^processor /proc/cpuinfo)" | bc) -eq 1 ] returns true if the current machine load is at least equal to the number of CPUs. If either of the tests returns true we wait 10 seconds and check again. If both tests return false, i.e. 2GB are available and machine load falls below number of CPUs, we start our command and save it's output in a text file. The ( ( ... ) & ) construct lets the command run in background even if we log out. See http://www.commandlinefu.com/commands/view/3115/ .

See udev at work
See how your system works with pendrives/mice/monitors/whatever-you-can-plug-in. Use cases: see on which /dev/... your peripherals are, find out if a specific udev rule is being applied correctly.

AWK Calculator

Figure out what shell you're running

a trash function for bash
Every rm'ed a file you needed? Of course you haven't. But I have. I got sick of it so I created a bash function. Here it is. It'll put trashed files into a $HOME/.Trash/"date" folder according to the date. I have rm aliased to it as well in my bashrc so that I still use the rm command. It'll choke if you attempt to trash a directory if that directory name is already in the Trash. This rarely happens in my case but it's easy enough to add another test and to mv the old dir if necessary. function trash(){ if [ -z "$*" ] ; then echo "Usage: trash filename" else DATE=$( date +%F ) [ -d "${HOME}/.Trash/${DATE}" ] || mkdir -p ${HOME}/.Trash/${DATE} for FILE in $@ ; do mv "${FILE}" "${HOME}/.Trash/${DATE}" echo "${FILE} trashed!" done fi }

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