Search and replace with sed when dots and underscores are present

Question

How do I replace foo. with foo_ with sed simply running

sed \'s/foo./foo_/g\' file.php

doesn\'t work. Thanks!

Answer 1

Escape the dot with a \

sed 's/foo\./foo_/g' file.php

If you find the combination of / and \ confusing you can use another 'separator' character

sed 's#foo\.#foo_#g

The 2nd character after the s can be anything and sed will use that character as a separator.