http://fahdshariff.blogspot.cz/2012/12/sed-mutli-line-replacement-between-two.html
Sed: Mutli-Line Replacement Between Two Patterns
This post has some useful sed commands which can be used to perform replacements and deletes between two patterns across multiple lines. For example, consider the following file:
$ cat file
line 1
line 2
foo
line 3