[SOLVED] regex if conditionals

vincix · 05-26-2019, 12:43 PM

Code:

grep "^Subject:" emaillist.mbox
Subject: Project-specific sitemap for build server content
Subject: Re: Project-specific sitemap for build server content
Subject: [Hosting] ns2.osuosl.org maintenance - June 11,
grep "^From:" emaillist.mbox
From: Ken <k23423@ethercloud.io>
From: Gavin <g23432423@ethercloud.io>
From: Music <m23423423@ethercloud.io>

And I'm trying this to match the From and Subject lines:

Code:

grep -Po '((?<subj>Subject)|(?<from>From)): (?(subj).+|?(from)\w+? <\w+?@\w+?\.\w{1,63}>)' emaillist.mbox
grep: nothing to repeat

I'm not sure exactly what I'm doing wrong.

pan64 · 05-26-2019, 12:46 PM

I don't understand what do you want to achieve, but you can definitely try: https://regex101.com/

vincix · 05-26-2019, 01:00 PM

I'm simply testing if conditionals on a file, that is to say, only display lines beginning with "From" and lines beginning with "Subject" and the string that follows. For "Subject: " it would be anything, for "From: " I'd match the format that can be found in the lines themselves: string <email@format.com>

Indeed, testing it on the site showed me what the problem was. It didn't like the |? because I have to place a bracket before it as in (?
So the correct way seems to be:

Code:

((?<subj>Subject)|(?<from>From)): (?(subj).+|(?(from)\w+? <\w+?@\w+?\.\w{1,63})>)

So nothing to repeat meant that I was trying to associate ? with a pipe, which didn't make sense, of course.