UNIX/Linux - Command Line Tips

Command	Description
du -hs dir	Displays disk usage of dir. -h gives human readable format (e.g. 12M) and -s suppresses every recursive directory's output
echo $?	Displays the return code of the previously exited program
pgrep -lf process_name	Displays pid of all running processes named process_name. -l lists the process name and -f matches in the full command line