Re: Fix testsuite errors due to shell quoted parameter expansion issue.

[Mikael Magnusson <mikachu@gmail.com>]

On 3 August 2010 22:55, Eric Blake <eblake@redhat.com> wrote:
> [adding autoconf to document some shell bugs]
>
> On 08/03/2010 02:32 PM, Ralf Wildenhues wrote:
>> Interesting shell unportability:
>>
>> $ bash -c 'f=" val" e=; echo "$e"$f'
>> val
>> $ ksh -c 'f=" val" e=; echo "$e"$f'
>>  val
>>
>> ksh93, dash, zsh all do it like ksh.  Is that a bug in bash?
>
> Yes; adding bug-bash accordingly.  According to POSIX:
>
> http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_05
>
> "After parameter expansion ( Parameter Expansion ), command substitution
> ( Command Substitution ), and arithmetic expansion ( Arithmetic
> Expansion  ), the shell shall scan the results of expansions and
> substitutions that did not occur in double-quotes for field splitting
> and multiple fields can result."
>
> Since $f is not quoted, its expansion must undergo field splitting.  But
> since "$e" is quoted, it must not be elided even though empty.  The
> result must be _two_ fields, as if you had done "echo '' 'val'".
>
> But it is _also_ a bug in zsh; adding zsh-workers accordingly.
>
> $ zsh -cvx 'f=" val" e=; echo "$e"$f'
> +zsh:1> f=' val' e=''
> +zsh:1> echo ' val'
>  val
>
> Oops - zsh only passed one argument to echo, with a leading space,
> instead of passing an empty argument and letting echo supply the space.
>  ksh93, pdksh, and dash get it right (although dash doesn't use quotes
> in -vx output, hence my use of n() to force things to tell; n() is
> another way to expose the bash and zsh bugs).

zsh doesn't do word splitting by default, you can enable it with the = modifier:
% zsh -fcvx 'f=" val" e=; echo "$e"$=f'
+zsh:1> f=' val' e=''
+zsh:1> echo '' val
 val

does what you want

Alternatively you can make zsh try to be closer to sh by setting
argv[0] to sh when executing it, or running 'emulate sh' as the first
command (and possibly other ways I don't know about):
% zsh -fcvx 'emulate sh;f=" val" e=; echo "$e"$f'
+zsh:1> emulate sh
+zsh:1> f=' val' e=''
+zsh:1> echo '' val
 val

There's also --shwordsplit for this specific case:
% zsh --shwordsplit -fcvx 'f=" val" e=; echo "$e"$f'
+zsh:1> f=' val' e=''
+zsh:1> echo '' val
 val

(the -f above only avoids loading my .zshenv which would spam my output)

-- 
Mikael Magnusson