Path: csiph.com!xmission!news.snarked.org!news.linkpendium.com!news.linkpendium.com!panix!usenet.stanford.edu!not-for-mail From: Chet Ramey Newsgroups: gnu.bash.bug Subject: Re: Misbehavior with constants and bash script Date: Mon, 19 Nov 2018 18:38:12 -0500 Organization: ITS, Case Western Reserve University Lines: 73 Approved: bug-bash@gnu.org Message-ID: References: <857e2280-38c5-344e-1916-17a6c6c61b02@netsystem.de> Reply-To: chet.ramey@case.edu NNTP-Posting-Host: lists.gnu.org Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="KEuOBqHOJNVXV8DZJizZslXa3PJNHGilQ" X-Trace: usenet.stanford.edu 1542670718 30440 208.118.235.17 (19 Nov 2018 23:38:38 GMT) X-Complaints-To: action@cs.stanford.edu Cc: chet.ramey@case.edu To: Alexander Reintzsch , "bug-bash@gnu.org" Envelope-to: bug-bash@gnu.org X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:reply-to:cc:subject:to:references:from:openpgp :autocrypt:organization:message-id:date:user-agent:mime-version :in-reply-to; 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charset=utf-8 Content-Transfer-Encoding: quoted-printable On 11/19/18 3:04 PM, Alexander Reintzsch wrote: > Hello, >=20 > I think I have found some unexpected behavior related to constants in > bash scripts. I have attached the short proof of concept bash script. >=20 > Usually bash scripts continue when they face an error with one command > but this script shows some weired behavior. It exits all the functions > it has called without executing the remaining commands and the continue= s > to run in the top scope of the script. >=20 > This only happens when a constant declared with > declare -r myConst=3D"myConstantValue" > is attempted to be redefined using > myConst=3D"new value" > but not with > declare myConst=3D"new value" >=20 > This behavior doesn't seem right. OK, let's unpack this. The variable assignment without declare has the posix semantics, in that it constitutes a variable assignment error. When the shell is in posix mode, it exits. When not in posix mode, the shell returns to the top leve= l and continues execution. It could return to the previous execution contex= t -- a virtual `return' -- or exit as it does in posix mode but has never done so. When the assignment is used as an argument to `declare', it causes the declare command to fail, but it's not a variable assignment error, so the script simply continues as with any other failed command. --=20 ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/= --KEuOBqHOJNVXV8DZJizZslXa3PJNHGilQ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iF0EARECAB0WIQR8ATX7CIqvbGbGULm7WGnwZOp0qwUCW/NJcgAKCRC7WGnwZOp0 q8v+AJ9mjbKin9hZDpHMc7PlVo00kDTikwCdHW0OD3d4bmbpQbvL16M/0lMviZI= =OLGL -----END PGP SIGNATURE----- --KEuOBqHOJNVXV8DZJizZslXa3PJNHGilQ--