Using sed to delete range of lines except the end pattern

Question

input.txt:

blah1
blah2
start_pattern
blah3
blah4
blah5
end_pattern
blah6
blah7

I would like input.txt to become:

blah1
blah2
end_pattern
blah6
blah7

I tried the following, but it didn't work.

sed -i "/start_pattern/, /end_pattern/{$!d}" input.txt

Answer 1

This question deals with your problem:

$ sed '/start_pattern/,/end_pattern/{/end_pattern/!d}' foo.txt
blah1
blah2
end_pattern
blah6
blah7