Commands

Unpack a tar file

tar xvzf file.tar.bz2

Send an e-mail from shell

echo message | mutt -s "Birthday celebration" -a citymap.jpg -- all@friends.org

Copy only staged files from git preserving directory structure

cp --parents `git diff --name-only --staged` ~/directory

Merge many PDF files into one:

pdftk *.pdf cat output combined.pdf verbose

Find out working directory of given process

ps aux | grep {process-name}
pwdx 13456