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From: =?UTF-8?B?TMOpYSBHcmlz?= <lea.gris@noiraude.net>
Newsgroups: gnu.bash.bug
Subject: Explicit variables declaration statements do not resolve back-references from same statement
Date: Wed, 24 Jul 2019 20:01:28 +0200
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From: =?UTF-8?B?TMOpYSBHcmlz?= <lea.gris@noiraude.net>
To: bug-bash@gnu.org
Message-ID: <fa53376b-927b-a37b-bb4d-ff0ebd7e25bf@noiraude.net>
Subject: Explicit variables declaration statements do not resolve
 back-references from same statement

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Found this strange behavior difference in Bash, between explicit and=20
implicit declarations of variables.

An implicit variables declaration statement resolve back-references to=20
variables from the same statement.

Whereas:

An explicit variables declaration statement does not resolve=20
back-reference variables from the same statement.

Illustration code:

=3D=3D=3D=3D knip code start
#!/usr/bin/env bash

unset a b c
printf $'\nExplicit declarations statements:\n'
printf $'\ntypeset -i a=3D2 b=3D$a c=3D"$((a - 1))":\n=3D> '
typeset -i a=3D2 b=3D$a c=3D"$((a - 1))"
printf 'a=3D%d b=3D%d c=3D%d\n' "${a}" "${b}" "${c}"
unset a b c
printf $'\ndeclare a=3Dhello b=3Dworld c=3D"$a $b":\n=3D> '
declare a=3D'hello' b=3D'world' c=3D"${a} ${b}"
printf $"a=3D'%s' b=3D'%s' c=3D'%s'\\n" "${a}" "${b}" "${c}"

unset a b c
printf $'\nImplicit declarations statements:\n'
a=3D2 b=3D$a c=3D"$((a - 1))"
printf $'\na=3D2 b=3D$a c=3D"$((a - 1))":\n=3D> '
printf 'a=3D%d b=3D%d c=3D%d\n' "${a}" "${b}" "${c}"
unset a b c
a=3D'hello' b=3D'world' c=3D"${a} ${b}"
printf $'\na=3Dhello b=3Dworld c=3D"$a $b":\n=3D> '
printf $"a=3D'%s' b=3D'%s' c=3D'%s'\\n" "$a" "$b" "$c"
=3D=3D=3D=3D knip code end

Output:
> Explicit declarations statements:
>=20
> typeset -i a=3D2 b=3D$a c=3D"$((a - 1))":
> =3D> a=3D2 b=3D2 c=3D1
>=20
> declare a=3Dhello b=3Dworld c=3D"$a $b":
> =3D> ./b.sh[10]: declare: not found [Aucun fichier ou dossier de ce typ=
e]
> a=3D'' b=3D'' c=3D''
>=20
> Implicit declarations statements:
>=20
> a=3D2 b=3D$a c=3D"$((a - 1))":
> =3D> a=3D2 b=3D2 c=3D1
>=20
> a=3Dhello b=3Dworld c=3D"$a $b":
> =3D> a=3D'hello' b=3D'world' c=3D'hello world'

ksh93 resolves explicit back-references with typeset.

--=20
L=C3=A9a Gris


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