.		current dir
~		user HOME
..		upper dir
TAB		command tab completion
ls		list files and dir HERE; ls; ls ~; ls ~/0214
mkdir		make a directory; mkdir 0224; mkdir ./dir
cd		change directory; cd; cd ~/0214
touch		new file size 0; touch ~/0214/foo
rm		delete a file; rm ~/0214/foo; rm -fr dir/; 
rmdir		delete a dir; rmdir dir/