sed - comment a matching line and x lines after it

Question

I need help with using sed to comment a matching lines and 4 lines which follows it. in a text file.

my text file is like this:

[myprocess-a]
property1=1         


        

Answer 1

Using string concatenation and default action in awk.
http://www.gnu.org/software/gawk/manual/html_node/Concatenation.html

awk '/myprocess/{f=1} f>5{f=0} f{f++; $0="#" $0} 1'  foo.txt

or if the block always ends with empty line

awk '/myprocess/{f=1} !NF{f=0} f{$0="#" $0} 1'  foo.txt