processing passwords?

[Jay Ashworth]

----- Original Message -----
> From: "Jean-Pierre A. Radley" <appl at jpr.com>
> To: "FilePro Mailing List" <filepro-list at lists.celestial.com>
> Sent: Monday, October 15, 2012 5:19:58 PM
> Subject: Re: processing passwords?
> Jay Ashworth propounded (on Mon, Oct 15, 2012 at 05:09:59PM -0400):
> | ----- Original Message -----
> | > From: "Jean-Pierre A. Radley" <appl at jpr.com>
> |
> | > | KENMAGIC=1; export KENMAGIC
> | >
> | > Why the superflous, unnecessary semi-colon?
> |
> | export means "make the named variable visible to child processes;
> | doing an assignment in front of a command makes it visible to *that*
> | processes, but *not* in the environment of the shell running that
> | process; I've never been clear on the semantics of the first. So
> | since
> | I *always* want it set in the current process as well as its
> | children,
> | I do the assignment and the export as separate commands.
> 
> An assignment exists in the environment of the shell in which it is
> made.
> An assignment preceding a command makes it exist in the command's
> environment too.
> Since the command in this case an "export" of that assignment, the
> assignment persists in the environment of the shell in which it was
> made as well as in all of that shell's children.

Not quite.

==================8<====================
jra at princeton:~> unset JRA            # make sure the variable isnt set.
jra at princeton:~> JRA=test echo $JRA   # set it in the environment of echo
                                      # find out that it wasn't set by the time
                                      # the statement was parsed
jra at princeton:~> echo $JRA            # how bout now?
                                      # still not set
jra at princeton:~> JRA=test bash        # try inline with a subshell
jra at princeton:~> echo $JRA            
test                                  # INSIDE THE SUBSHELL, it's set
jra at princeton:~> exit                 # exit the subshell
jra at princeton:~> echo $JRA            # set up top?
                                      # no, as expected.
jra at princeton:~>

==================8<====================

So the important part of your second assertion:

> An assignment preceding a command makes it exist in the command's
> environment too.

is, as my memory led me to believe, incorrect: assignments which precede
a command name on the command line do *not* affect the environment of the
shell which processes them, only that of the command specified.  I myself
had not realized that the shell parsed the command line before setting 
up the child environment and running it, which is why 

$ JRA=test echo $JRA 

does not work in the superficially obvious manner, but it makes sense
after I think about it -- it's like trying to use sudo with redirection.

That behavior is documented back to the v7 shell, I'm pretty sure, though
my v7 UPM is at home.

Cheers,
-- jra
-- 
Jay R. Ashworth                  Baylink                       jra at baylink.com
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