Comment out/delete blocks in large amount of files - regex

Question

I'm attempting to write something that can process Nagios config files containing a block of text, and either add # to the start of each line, or delete the block. (To function as a kind of mass check removal in Nagios itself).
Ex:
define service {
service_description Service 1
use Template 1
host_name Host 1
check_command Command A
}
define service {
service_description Service 2
use Template 1
host_name Host 1
check_command Command B
}
define service {
service_description Service 3
use Template 1
host_name Host 1
check_command Command C
}
Would need to change to this (or equivalent):
define service {
service_description Service 1
use Template 1
host_name Host 1
check_command Command A
}
#define service {
# service_description Service 2
# use Template 1
# host_name Host 1
# check_command Command B
#}
define service {
service_description Service 3
use Template 1
host_name Host 1
check_command Command C
}
Is there a way to regex match the block between "define service {" and "}", and containing either "Service 2" or "Command "B", and append/delete the block via sed/awk/perl, etc?
Thanks.

Answer 1

sed '
# take each paragraph one by one
/define service {/,/}/{
# inside paragraphe, add each line (one at a time) in buffer
H
# if not the end of paragraphe, delete the line (from output) (and cycle to next line)
/}/!d
# empty current line (the last of paragraphe) and swap with the whole buffer
s/.*//;x
# if it contain Service2 (and Command B on next line) goto to label comm
/Service2/ b comm
/Command B/ b comm
# goto label head (so no Service2 nor command b in paragraphe)
b head
:comm
# comment each line of paragraphe (multiline with \n as new line)
s/\n/&#/g
: head
# remove first character (a new line due to use of H and not h on first line)
s/.//
}
# default behaviour that print the content
' YourFile
Self commented

Answer 2

Here's a regex that creates the match you want:
/define service\s\{.*(Service 2|Command B).*\}/s
You can test it here. I have no experience with sed, awk or perl, so I will not make any attempt to create a replacement.

Answer 3

sed -n '/define service {/,/}/{:1;N;/\}/!b 1;/Command B\|Service 2/{s/\n/\n#/g;s/^/#/g;p;d;b 1};p;d;b 1}' file_name
This is how it works
picks the block within braces;keeps appending to pattern space till a closing brace is found;searches the patter space for the two key words; if found then appends a # in front of every new line in pattern space and prints the content. Clears the pattern space and repeats the provess