Replace a Function Name in Drupal Source Files

> perl -i -pe 's/oldname_/newname_/g' `find | grep "\.module$"`

Or if you want to first check the results:

> perl -pi.bak -e 's/oldname_/newname_/g' `find | grep "\.module$"`

which will create backup of original files. Those you can delete later with:

> find . -name "*.bak" -exec rm -rf {} \;

You can replace ".module" with ".inc" or "tpl\.php" if you also need those processed