RE: Export problem

["Andrej Borsenkow" <Andrej.Borsenkow@mow.siemens.ru>]

>
> > - in ${x:=word} word is *never* splitted irrespectively of
> where it appears
> > and if it is quoted
>
> Where is that stated?
>

Nowhere. You misunderstand the basic concept of field splitting in sh. I
suspect, it is a result of incorrect implementation of splitting in zsh.

Field Splitting is the step in processing of command line. It happens
*after* parameter substitution. It means, that ``word'' in ${x:=word} is
never splitted - the *result* of this substitution as a whole may possibly
be splitted.

> > - x=word is not splitted (should I add "never"?)
>
> Where is that stated?
> Your quote of SUS (which is lifted from POSIX) said
> that each variable assignment undergoes expansion
> in step 4, including parameter expansion and command
> substitution.  In addition, the bit about Field Splitting
> says that "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."
> It then goes on to talk about IFS and how splitting
> is to occur.  I also don't see any exceptions or
> proscriptions against splitting when variable assignment
> is involved.
>

It does not say "the shell scans the result of *every* expansion ...".
Please, understand - splitting in sh does not happen as part of
variable/command substitution. It happens after these substitutions have
been done. The above simply means that in ``IFS=:; ls a:b${foo}'' the a:b
will *not* be splitted even though IFS is set to ``:''. But ${foo} possibly
will. That is also correctly implemeted by zsh and bash.

> > - in export x=word the whole `x=word' is field splitted unless quoted.
>
> That seems fairly straight-forward, but I don't understand the
> intended effect.  The output of field splitting is "fields."
> The input is whatever results from the expansion or substitution
> of "words."  Does POSIX define these things?
>

Yes. Please, look in grammar for definition of WORD, look here
<http://www.opengroup.org/onlinepubs/007908799/xcu/chap2.html#tag_001_006>
for precise definition how expansions are performed and look in my previous
mail for definition how fields are used (first field becomes command name,
subsequent fields become arguments).

> If `date +%z%f` expanded to "-0400; rm -rf .", what should
>
> export THIS=`date +%z%f` do?
>
> a) export THIS with the value "-0400; rm -rf ."
> b) export THIS with the value "-0400; rm -rf ." as an array of 4 words?
>    POSIX doesn't seem to acknowledge the concept of arrays in the Shell
>    Command Language.
> c) export THIS with the value "-0400;" and try to export parameters
>    named "rm", "-rf", and "."?

One answer for all - it should execute command ``export'' with parameters:

THIS=-0400;
rm
-rf
.

What the command ``export'' does with these parameters - it is up to this
command.

> d) retokenize the line and treat it as a sequential list of two commands?
>

Oh, no! Please :-)

-andrej