I want to filter some of the mail IDs returned by mailq
(Postfix). However, the format is not very "grep-friendly", since the information for a single mail spans multiple lines:
9F701869D2 1356 Mon Aug 23 12:13:43 some@sender
(host some.host[1.2.3.4] said: 450 4.1.1 some error message)
some@recipient
9437586CF4 3153 Sat Aug 21 09:36:40 some@other.sender
(host some.host[1.2.3.4] said: 450 4.1.1 some error message)
some@other.recipient
What's the easiest way to get, for example, all mail IDs where some particular error code occurred? Maybe by removing the (single) newlines, then grep
ing and then cut
ing? Or by using some other, more suitable tool?
Please explain your answer. My main interest is not a copy-and-paste solution for my current problem (filtering by error code), but rather understanding how to easily parse such multi-line output.
Best Answer
What about:
grep -C 1 said:
-C is context and returns one line before & after "said:". Also, for future reference, -A is for after, -B is for before.
grep -C 1 said: | grep ^[0-9] | cut -f1 -d " "
(for the list of IDs)
If you need something more complex, then you would have to use awk.