On Fri, 18 Oct 2002, Andrew DeFaria wrote:
> John Vincent wrote:
>
> > Hi,
> >
> > Not quite right there ... You can preceed a command with an
> > assignment, and the assigned variable is then put into the environment
> > of the command that is run. Thus the command
> > "echo" is run with an environment variable AAAA with the value aaaa.
> > However, this does not change the AAAA shell variable (which is
> > currently empty) so the echo prints a blank (it's empty argument) and
> > ignores the AAAA in it's environment.
> >
> > This syntax is useful for setting environment variables for one
> > command invocation only. They are not saved.
> >
> > I hope this fully explains what is going on.
>
> It doesn't. If "This syntax is useful for setting environment variables
> for one command invocation only" then the echo command should have
> echoed "aaa". Otherwise the syntax is not useful for setting environment
> variables for one command invocation. Perhaps what is meant is that this
> syntax is useful for overriding environment variables for one command
> invocation? However this leaves a glaring inconsistancy prone to error
> if the variable was not set already then no override takes place.
Andrew,
[pechtcha:~] AAAA=aaa && echo $AAAA
aaa
[pechtcha:~] AAAA=aaa echo $AAAA
[pechtcha:~] AAAA=aaa eval 'echo $AAAA'
aaa
[pechtcha:~] AAAA=aaa sh -c 'echo $AAAA'
aaa
[pechtcha:~]
Does this help?
Igor
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