In place replacements
In GNU sed: use -i without arg.
sed -i -e 's/foo/bar/' example.md
In OSX, -i '' is required.
sed -i '' -e 's/foo/bar/' example.md
File regions
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'