From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 16852 invoked from network); 3 Mar 2023 19:26:53 -0000 Received: from minnie.tuhs.org (2600:3c01:e000:146::1) by inbox.vuxu.org with ESMTPUTF8; 3 Mar 2023 19:26:53 -0000 Received: from minnie.tuhs.org (localhost [IPv6:::1]) by minnie.tuhs.org (Postfix) with ESMTP id C78D9434A3; Sat, 4 Mar 2023 05:26:52 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tuhs.org; s=dkim; t=1677871612; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references:list-id:list-help:list-owner:list-unsubscribe: list-subscribe:list-post; bh=V+h0/TRyrQ1D6P0mhZ+wLdW+c0gf28Kh63oxkjad0ns=; b=oLrhAWvFlJFUQwVyW8axzOoWvmlS6JVkVXr2Vb5/1O2HGQ0fL2pohtrWaQWj9B+IM5GO2D v6TSCntSt2pfzZDFpIzk5ifJvedn7uau59sfnAdVbjXlwZpVzB3jPv7KlynqBX7Sqr6pfl 5aoI5P+LP3k6wY7MZy7gcNT+Ig8gjGM= Received: from tncsrv06.tnetconsulting.net (tncsrv06.tnetconsulting.net [IPv6:2600:3c00:e000:1e9::8849]) by minnie.tuhs.org (Postfix) with ESMTPS id 501724334D for ; Sat, 4 Mar 2023 05:26:49 +1000 (AEST) Received: from Contact-TNet-Consulting-Abuse-for-assistance by tncsrv06.tnetconsulting.net (8.15.2/8.15.2/Debian-3) with ESMTPSA id 323JQmtu007471 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NO) for ; Fri, 3 Mar 2023 13:26:48 -0600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tnetconsulting.net; s=2019; t=1677871608; bh=V+h0/TRyrQ1D6P0mhZ+wLdW+c0gf28Kh63oxkjad0ns=; h=Subject:To:References:From:Message-ID:Date:User-Agent: MIME-Version:In-Reply-To:Content-Type:Cc:Content-Disposition: Content-Language:Content-Transfer-Encoding:Content-Type:Date:From: In-Reply-To:Message-ID:MIME-Version:References:Reply-To: Resent-Date:Resent-From:Resent-To:Resent-Cc:Sender:Subject:To: User-Agent; b=oQ2Ic6ThztF6xswioZQC7rRTYd7473NCT4SxTPqFFgldEMlqCogYL9s22FEdEXblG WACkUAiscak640Cd9yjVFcAx8/GkIJo3aIqDC2UVulVb4ZLkTGdMOan2fxq8LeRT2f fx41poRffbO/4AsEHLB4C0haO3dM6PgiyzUBE250= To: coff@tuhs.org References: <8d1de5c8-1f34-3d37-395d-0f1da7b062ec@spamtrap.tnetconsulting.net> <688396c8-7a25-5cd6-282c-49f1b13117d4@spamtrap.tnetconsulting.net> <1519cce3-1c38-8a9c-cfdd-b39484bd163b@spamtrap.tnetconsulting.net> Organization: TNet Consulting Message-ID: <9bb089cd-1317-6bcf-3bd3-231ce96b333c@spamtrap.tnetconsulting.net> Date: Fri, 3 Mar 2023 12:26:41 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="------------ms040601020804090801030406" Message-ID-Hash: YCX4ZQ4KCZQ56MEXX4MKETLZRFBFXCH3 X-Message-ID-Hash: YCX4ZQ4KCZQ56MEXX4MKETLZRFBFXCH3 X-MailFrom: gtaylor@tnetconsulting.net X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.6b1 Precedence: list Subject: [COFF] Re: Requesting thoughts on extended regular expressions in grep. List-Id: Computer Old Farts Forum Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: From: Grant Taylor via COFF Reply-To: Grant Taylor This is a cryptographically signed message in MIME format. --------------ms040601020804090801030406 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 3/3/23 6:47 AM, Dan Cross wrote: > Oh, for sure; to be clear, it was obvious that in the earlier=20 > discussion the original was just part of something larger. Good. For a moment I thought that you might be thinking it was stand alo= ne. > FWIW, this RE seems ok to me; the additional context makes it unlikely = > to match something else accidentally. :-) > It needn't be special. The point is simply that there's some external = > knowledge that can be brought to bear to guide the shape of the REs. ACK I've heard "domain (specific) knowledge" used to refer to both extremely = specific training in a field and -- as you have -- data that is having=20 something done to it. > In this case, you know that log lines won't begin with `___ 123=20 > 456:789` or other similar junk. They darned well had better not. > Kinda. The "machine" in this case is actually an abstraction, like a=20 > Turing machine. The salient point here is that REs map to finite state = > machines, and in particular, one need not keep (say) a stack of prior=20 > states when simulating them. Note that even in an NDFA simulation,=20 > where one keeps track of what states one may be in, one doesn't need=20 > to keep track of how one got into those states. ACK > Obviously in a real implementation you've got the program counter,=20 > register contents, local variables, etc, all of which consume=20 > "memory" in the conventional sense. But the point is that you don't=20 > need additional memory proportional to anything other than the size=20 > of the RE. DFA implementation could be implemented entirely with=20 > `switch` and `goto` if one wanted, as opposed to a bunch of mutually=20 > recursive function calls, NDFA simulation similarly except that=20 > you need some (bounded) additional memory to hold the active set=20 > of states. Contrast this with a pushdown automata, which can parse=20 > a context-free language, in which a stack is maintained that can=20 > store additional information relative to the input (for example,=20 > an already seen character). Pushdown automata can, for example,=20 > recognize matched parenthesis while regular languages cannot. I think I understand the gist of what you're saying, but I need to=20 re-read it and think about it a little bit. > Anyway, sorry, this is all rather more theoretical than is perhaps=20 > interesting or useful. Apology returned to sender as unnecessary. You are providing the requested thought provoking discussion, which is=20 exactly what I asked for. I feel like I'm going to walk away from this=20 thread wiser based on the thread's content plus all additional reading=20 material on top of the thread itself. > Bottom line is, I think your REs are probably fine. `egrep` will=20 > complain at you if they are not, and I wouldn't worry too much about=20 > optimizing them: I'd "stop" whenever you're happy that you've got=20 > something understandable that matches what you want it to match. Thank you (again) Dan. :-) --=20 Grant. . . . unix || die --------------ms040601020804090801030406 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCC CzowggUiMIIECqADAgECAhEAw8IZWQHDVuWWKHZeojBgoDANBgkqhkiG9w0BAQsFADCBljEL MAkGA1UEBhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2Fs Zm9yZDEYMBYGA1UEChMPU2VjdGlnbyBMaW1pdGVkMT4wPAYDVQQDEzVTZWN0aWdvIFJTQSBD bGllbnQgQXV0aGVudGljYXRpb24gYW5kIFNlY3VyZSBFbWFpbCBDQTAeFw0yMjExMTQwMDAw MDBaFw0yMzExMTQyMzU5NTlaMCsxKTAnBgkqhkiG9w0BCQEWGmd0YXlsb3JAdG5ldGNvbnN1 bHRpbmcubmV0MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAzOnBjTJUlBTzN81c PlYErJc9kEbTI/hXq0NA6ZoG4VM6puYTEXtITANjgX+NRwwHjldESnC8dvh6Mx5ckEk9sWoD l8Yr/dWhF3s4fGxAX5ziOeuBI/yX7rKJn6DOwclV3C6dyt3zrLB6LOiF4gA+lk/o3EbOwoPh 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