Run a Vim command on a bunch of files

gistfile1.txt

# For a bunch of Python files
vim -c "bufdo! set eventignore-=Syntax| %s/original/replacement/gce" *.py

# if you want to save as you go
vim -c "bufdo! set eventignore-=Syntax| %s/original/replacement/gce | update" *.py

# Breaking it down:
# bufdo! -> so that it doesn't complain about erroring
# set eventignore-=Syntax  -> so that every buffer gets syntax highlighting
# /gce  -> optional, global search in the line with confirmation and eating up the errors
# | update -> optional update to save every buffer as you move