processing passwords?

[Jean-Pierre A. Radley]

Jay Ashworth propounded (on Mon, Oct 15, 2012 at 05:35:02PM -0400):
| ----- 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.
| 

Your shell isn't behaving like mine, in that case. I start out in tcsh
and:

	jpradley:appl 6 sh
	$ unset JPR
	$ JPR=test echo $JPR

	$ echo $JPR
	test




-- 
JP