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dmarc=pass header.from=ntlworld.com; arc=none Received: from smtpq1.tb.ukmail.iss.as9143.net ([212.54.57.96]:34206) by zero.zsh.org with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) id 1oYkAS-0003yJ-QF; Thu, 15 Sep 2022 08:24:19 +0000 Received: from [212.54.57.81] (helo=smtp2.tb.ukmail.iss.as9143.net) by smtpq1.tb.ukmail.iss.as9143.net with esmtp (Exim 4.90_1) (envelope-from ) id 1oYkAS-0004NE-0p for zsh-users@zsh.org; Thu, 15 Sep 2022 10:24:16 +0200 Received: from oxbe15.tb.ukmail.iss.as9143.net ([172.25.160.146]) by smtp2.tb.ukmail.iss.as9143.net with ESMTP id YkARoBimQmIDmYkARo87B6; Thu, 15 Sep 2022 10:24:16 +0200 X-Env-Mailfrom: p.w.stephenson@ntlworld.com X-Env-Rcptto: zsh-users@zsh.org X-SourceIP: 172.25.160.146 X-CNFS-Analysis: v=2.4 cv=LoCBd1Rc c=1 sm=1 tr=0 ts=6322e130 cx=a_exe a=3VDdwIuOneLoWcGUQKPbfw==:117 a=1DWFKdCB1IcA:10 a=IkcTkHD0fZMA:10 a=ZjyAdWuDOD4A:10 a=22Ro6XbQAAAA:8 a=n1SsW5UZFMwilJ3YpWoA:9 a=QEXdDO2ut3YA:10 a=p1RiBf0vZFgkX3Jmbd9N:22 X-Authenticated-Sender: p.w.stephenson@ntlworld.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ntlworld.com; s=meg.feb2017; t=1663230256; bh=BKfCApzc4ZNaArBGlEhDvxXyieEEuqd4hOrPnXFpX+A=; h=Date:From:To:In-Reply-To:References:Subject; b=f8gUMksptevf9xXnb6Et33/QrzGkRbqcWxV+V/PKXlPmiU0SUwFXw17LGGKMpXZbF DY6V46XiCR/PI5K0nRjFT/gttqLGIqpTesFjZeC17ZoiQOgdyDHRE4EPklCzrf28YW g0aXINV4gaXSn/f7FrmCWwyX0VQpRGIfKENDq7uOxsq5QvTlzESKeUFNzpUkV9Jllp 9iq3ngmXxUnNsdJst9N98+zbDUza74OVqJLSk7ncIWWAuLCXwbmucBPfIqXYg1lppi y59NFxI29/fNgH5yVc0nXi7wO1DeV8d9/iHOIk8E968MQthXFNriogCk3GBbnw/ybu zRRXvaVd5sKjQ== Date: Thu, 15 Sep 2022 09:24:15 +0100 (BST) From: Peter Stephenson To: zsh-users@zsh.org Message-ID: <1026093540.752006.1663230255721@mail.virginmedia.com> In-Reply-To: References: <5dc8b935-f234-ca54-0ceb-50cb1da9bc29@rayninfo.co.uk> Subject: Re: Can I test if a parameter expansion has worked MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Priority: 3 Importance: Normal X-Mailer: Open-Xchange Mailer X-Originating-IP: 147.161.224.167 X-Originating-Client: open-xchange-appsuite X-CMAE-Envelope: MS4xfNguKe7seps42cXzOyApK3LEfJaxnYUtGqiEmdSlOTCbuKBNuZc40I6oNrT6LJS2xyUhROOQ4Zw80XBiGqQ3ZmXprmfVQRe9r5jnw7j+mvpNlZbr+oFz O7/s73HO8y9dTkwvjskldFcRh7PBftPzp7XGCkCoHZ+hQhGsS8z45I5PpD8JKSykP7L3iapmWMKiuBOPIuPIAWPkjH5+lOHY4DRT5xPbXUUzhds+8bkBZ6Mg X-Seq: 28081 Archived-At: X-Loop: zsh-users@zsh.org Errors-To: zsh-users-owner@zsh.org Precedence: list Precedence: bulk Sender: zsh-users-request@zsh.org X-no-archive: yes List-Id: List-Help: List-Subscribe: List-Unsubscribe: List-Post: List-Owner: List-Archive: > On 15/09/2022 08:34 zzapper wrote: > # adding a prefix '_s' to an image name >=20 > f=3Dstuff.jpg; >=20 > print ${f/%(#m).[pjg][npi]e#[gf]/_s$MATCH} >=20 > stuff_s.jpg=C2=A0 # good this is what i want >=20 > # now pass 'bad' input >=20 > f=3Dstuff.txt; >=20 > print ${f/%(#m).[pjg][npi]e#[gf]/_s$MATCH} > stuff.txt=C2=A0 #=C2=A0 expansion has obviously left the input unchanged = but can I=20 > test for that??? No, there's no way of telling if some expansion actually changed an expression without actually testing the final result. The differences between the cases (changed / not changed) are buried deep within the shell and don't leave an obvious trace above --- and in any case given how complicated zsh expressions can get finding a useful binary way of testing what the whole expression did would be incredibly hairy. Just test the resulting expression. pws