I am using regex to match patterns in my log. I need to match pattern at the beginning, but then invert the match, ie:
I need to match this line:
reject: RCPT from unknown[165.231.143.153]: 450 4.7.25 from=<spameri@tiscali.it> to=<spameri@tiscali.it>
But not this line:
reject: RCPT from unknown[165.231.143.153]: 450 4.7.25 from=<spameri@tiscali.it> to=<alice@mydomain.com>
Basically, if the line contains to=<alice@mydomain.com>
(or any other email address with mydomain.com
, then it should not trigger a match. Otherwise if it is anything else, ie to=<bob@otherdomain.com>
, or to=<alice@thirddomain.com>
then it should match.
I tried using this negative look ahead pattern:
'^reject: RCPT from [A-Za-z0-9\.-]+\[{ip}\]: .* to=<[A-Za-z0-9\._-]+@(?!mydomain.com)>',
where I am negating mydomain.com
using the construct the construct (?.mydomain.com)
How can I do that?
Lookaheads are non-consuming, ie the regex index remains where it was and the patterns matched are not added to the overal match value.
Thus, (?.mydomain.com)
in (?.mydomain.com)>
checks if there is no mydomain
, any char, com
immediately to the right of the current location, and as the next char must be >
, it is always true.
You need to consume the char before >
and thus you can use
^reject: RCPT from [A-Za-z0-9.-]+\[{ip}]: .* to=<[A-Za-z0-9._-]+@(?!mydomain\.com>)[^>]*>
Note you do not need to escape .
inside square brackets (aka character class) and you do not need to escape ]
when it is not inside a character class.
The @(?.mydomain\.com>)[^>]*>
matches
@
- a @
char (?.mydomain\.com>)
- not immediately followed with mydomain.com>
[^>]*
- (a negated character class matching) any zero or more chars other than >
>
- a >
char.
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