replacing multiple line pattern in sed

Question

I simply want to do following

replace

EXTRATHING {
};

by

SOMETHING {};

in inputfile. For this, I tried

sed -e 's/EXTRATHING {
};/SOMETHING/' input_file.txt  >outfile.txt

This doesn't work. Can someone suggest what would be the correct way of doing this with sed?

Answer 1

sed -n '1h;1!H;${;g;s/EXTRATHING {
};/SOMETHING {};/g;p;}' input_file.txt

would do it.

The problem with this is that it stores the whole input string in sed's buffer.

See sed and Multi-Line Search and Replace for more info, and a more efficient version.