find . -name '*.conf' | xargs grep -i 'url_de_monsite'
sed s/url_de_mon_site/new_url_de_mon_site/g fichier.conf > fichier.conf
find . -name '*.conf' -exec grep -qi 'url_de_mon_site {} && sed s/url_de_mon_site/new_url_de_mon_site/g {} > {};
find . -name "*.conf" -exec fgrep -i old_url \{\} \; -ok sed -i.bak 's/old_url/new_url/g' \{\} \;