Well, to be strictly conformant with heirloom SysV sh, we have to use the following (which is uglier than Cobol with a hangover):
#looper2-sh.sh
n=4
i=1
while [ $i -le $n ]
do
echo i = $i
i=`expr $i + 1`
done
which also works with dash and mksh. Perhaps this needs to go into a FAQ
somewhere about coding loops for an absolutely bare-bones shell.
> On 22 Apr 2015, at 00:22, Eric Blake <ebl...@redhat.com> wrote:
>
> On 04/21/2015 01:44 PM, Dr Alun J. Carr wrote:
>
>> Tests were done with bash, ksh, zsh, pdksh, dash and heirloom System V
>> Bourne sh with the following versions:
>> bash 3.2.57(1)
>> bash 4.3.33(1)
>> ksh version sh (AT&T Research) 93u+ 2012-08-01
>> zsh 5.0.5 (x86_64-apple-darwin14.0)
>> pdksh stable 5.2.14
>> dash stable 0.5.8
>> sh ???
>
> You do realize, I hope, that brace expansion is not required by POSIX,
> and therefore there is no standard for what behavior it has, and it
> should be no surprise that pdksh, dash, and Bourne sh do not try to
> expand it.
>
> As for whether bash should expand $n into 4 prior to doing brace
> expansion, or whether brace expansion is attempted first but not
> recognizing $n as a valid bound devolves into no expansion, that is
> indeed a difference between ksh and bash. But bash is consistent with
> its documentation:
>
>> The order of expansions is: brace expansion; tilde expansion, parameter
>> and variable expansion, arithmetic expansion, and command substitution
>> (done in a left-to-right fashion); word splitting; and pathname expanâ
>> sion.
>
> so you cannot use a variable as a bound and still expect brace expansion
> to work, since variables aren't expanded yet.
>
> --
> Eric Blake eblake redhat com +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
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