OSX Caveat

To do in place replacements -i '' is required (GNU/sed is different)

sed -i '' -e 's/foo/bar/' example.md

GNU/sed

To do in place replacements use -i without arg

sed -i -e 's/foo/bar/' example.md

Yes

Print until a certain line is met

sed '/begin api/q'

Print until a certain line is met, but not that line

sed '/^# begin/,$d'

Print everything after a given line

sed -n '/end api/,$p'