Grep, sed usage examples.

grep_sed_examples.sh

#!/bin/bash

# Recursively find all files that match a specific pattern
# and contain a specific string inside of it
grep -rl "SEARCH_FOR_WHAT" --include="*.htm" --include="*.html" /path/to/whatever

# And perform text replacement (in-line mode)
find . | xargs sed -i 's/BEFORE/AFTER/g'


# Using find instead of grep
find . -type f -name "*.htm" -o -name "*.html"