Re: handling of variables

[Peter Stephenson <pws@xxxxxxx>]

Michael Prokop wrote:
> Hello,
> 
> I'm just wondering about:
> 
> % zsh -f
> % FOO=BAR /bin/echo "$FOO"
> 
> %
> 
> Why doesn't this work? Am I running out of coffee? :)

The sequence of interepretation is

line gets parsed to <environment-assignment> <command+args>
line gets expanded to /bin/echo "" (assuming FOO is currently empty)
shell forks
FOO=BAR is put in the environment
shell execs /bin/echo ""

Compare this with the result of

FOO=BAR printenv FOO

where the command itself examines the environment.

> And I'm wondering what's happening at:
> 
> % zsh -f
> % FOO=BAR BAR=FOO echo $FOO $BAR
> 
> % FOO=BAR BAR=FOO echo $FOO $BAR
> BAR
> %

This looks suspiciously like a bug.  The value of BAR is being restored
after the echo, but the value of FOO isn't.

-- 
Peter Stephenson <pws@xxxxxxx>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070


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