When I use the su command in OS X's Terminal  say, to quickly switch to an administrator account to mount a drive using diskutil  the style of the command prompt changes.  Before using su, the Terminal's Darwin bash prompt displays my computer's name as dictated by the part of $HOSTNAME which precedes the part of that text string which reads .local, a colon, the current working directory, a space, the current user's name, and, finally, a dollar sign.  After running su, all that's displayed is bash-3.2$.  Is there a command that I could run to revert this without undoing my use of su?  
Maintaining the Current Style of the Command Prompt After Using 'su?'
osx;prompt;su
Run su -l $USERNAME via Terminal to log in as another user without losing your current prompt style.  