When using a command line interface, I like to see all the output a program makes. The standard out and error are already dumped to my console, but there is one piece of information usually hidden from the user: the return code.

Add the following to your .bashrc to get a nice notification if a program returns a non-zero code:

export PROMPT_COMMAND='ret=$?; if [ $ret -ne 0 ] ; then echo -e "returned \033[01;31m$ret\033[00;00m"; fi'

It looks like this: