Awk/sed script to convert a file from camelCase to underscores

Question

I want to convert several files in a project from camelCase to underscore_case.

I would like to have a onliner that only needs the filename

Answer 1

You could use sed also.

$ echo 'fooBar' | sed -r 's/([a-z0-9])([A-Z])/\1_\L\2/g'
foo_bar
$ echo 'fooBar' | sed 's/\([a-z0-9]\)\([A-Z]\)/\1_\L\2/g'
foo_bar