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From: Helmut Waitzmann <nn.throttle@xoxy.net>
Newsgroups: comp.unix.shell
Subject: Re: An interesting little quirk - difference between "bash" and "dash" (Linux)
Date: Sun, 05 Jan 2025 22:26:22 +0100
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 gazelle@shell.xmission.com (Kenny McCormack):
> $ bash -c 'foo=3Dbar;myfun() { local foo; echo "In myfun(), foo =3D $foo"=
; };myfun'
> In myfun(), foo =3D
> $ dash -c 'foo=3Dbar;myfun() { local foo; echo "In myfun(), foo =3D $foo"=
; };myfun'
> In myfun(), foo =3D bar
> $
>
> The difference is that in dash, the local foo picks up the value of the
> global foo, while in bash, it is empty.
>
> I'm not standards obsessed like some people in these newsgroups; I care
> more about desirable functionality.  In this case, I would not be surpris=
ed
> to hear that the dash behavior is more POSIX-ly correct,
>

 I guess, you won't be surprised to read that neither the bash nor=20
 the dash behavior is part of the POSIX standard.=20


> but it seems clear to me that the bash behavior is more
> desirable.
>
> I frequently use "local" precisely to ensure that I get a fresh,
> un-initialized variable.

 Bash won't give you an un=E2=80=90initialized variable.=C2=A0 It will give=
 you=20
 an modified, emptied variable, while dash will give you an=20
 unmodified variable.=20


 By the way, neither behavior will give you a fresh variable.=C2=A0 Try=20


   (
     for shell in bash dash
     do
       printf '\n%s:\n' "$shell"
       "$shell" -c '
         foo=3Dbar && readonly -- foo &&
         myfun()
         {
           local foo
           printf "In myfun(), foo =3D %s\n" "$foo"
           foo=3D
         } &&
         myfun' "$shell"
     done
   )