Stream editor. Similar to linux-cli-awk.
-i
means replace inplace.
s
means substitute. g
means global.
You can use any delimiter.
sed -i s%SITE_LOCATION=\"\$HOME/sites/lukerambling\"%SITE_LOCATION=\"\$HOME/sites/quartz\"%g ~/zettel/meta/shell/*.sh
Links
UNIX and Linux: sed | Panix
Learn sed: Definitive Guide to sed