processing passwords?

[Kenneth Brody]

On 10/16/2012 5:15 PM, Jean-Pierre A. Radley wrote:
> Kenneth Brody propounded (on Tue, Oct 16, 2012 at 10:49:46AM -0400):
> | On 10/15/2012 6:26 PM, Jean-Pierre A. Radley wrote:
[...]
> | > Your shell isn't behaving like mine, in that case. I start out in tcsh
> | > and:
> | >
> | > 	jpradley:appl 6 sh

I think I was partly thrown by not realizing that "jpradley:appl 6" was your 
prompt, and "sh" was the command you typed to start sh.

> | > 	$ unset JPR
> | > 	$ JPR=test echo $JPR
> | >
> | > 	$ echo $JPR
> | > 	test
> |
> | I hate to do it, but I have to side with Jay against JP on this one.  My
> | understanding has always been that "name=val command" sets the value of the
> | environment variable only for "command", and not in the shell.  It's been
> | this way since at least TRS-Xenix days.  In fact, "man sh" on my Linux box says:
> |
> | >        The  environment for any simple command or function may be
> | >        augmented  temporarily  by  prefixing  it  with  parameter
> | >        assignments,  as  described  above  in  PARAMETERS.  These
> | >        assignment statements affect only the environment seen  by
> | >        that command.
> |
> | What does "echo $JPR" say *before* the echo command?
>
> Don't follow you, Ken.
>
> The comand "JPR=test echo $JPR" produces just a newline.
>
> The next command shows that the assignment (JPR=test) before the command
> (echo $JPR) persists in the invoking shell, because the next command
> (echo $JPR) prints "test".

Note that I only get the behavior you show when using SCO's version of sh, 
and only if the command is a shell built-in, such as "echo".

========== SCO's /bin/sh
# echo $0
-sh
# unset JPR
# JPR=test echo $JPR

# echo $JPR
test
# unset JPR
# JPR=test ls -ld /tmp
drwxrwxrwt    4 bin      bin            8192 Oct 16 20:11 /tmp
# echo $JPR

#
========== SCO's /bin/bash
# bash
bash-2.05a# unset JPR
bash-2.05a# JPR=test echo $JPR

bash-2.05a# echo $JPR

bash-2.05a#
========== FreeBSD's /bin/sh
Moon5.6 (/dev/pts/0) > sh

Moon5.6 (/dev/pts/0) > ls -l /bin/*sh
-r-xr-xr-x  2 root  wheel  328384 Apr  9  2012 /bin/csh
-r-xr-xr-x  1 root  wheel  118512 Apr  9  2012 /bin/sh
-r-xr-xr-x  2 root  wheel  328384 Apr  9  2012 /bin/tcsh

Moon5.6 (/dev/pts/0) > unset JPR

Moon5.6 (/dev/pts/0) > JPR=test echo $JPR


Moon5.6 (/dev/pts/0) > echo $JPR


Moon5.6 (/dev/pts/0) >
========== Linux's /bin/sh (a symlink to bash)
Moon5.6 (/dev/pts/2) > sh

Moon5.6 (/dev/pts/2) > ls -l /bin/*sh
-rwxr-xr-x. 1 root root 877480 Jun 22  2010 /bin/bash
lrwxrwxrwx. 1 root root      4 Feb 29  2012 /bin/csh -> tcsh
-rwxr-xr-x. 1 root root 102216 Dec  2  2009 /bin/dash
lrwxrwxrwx. 1 root root      4 Mar  8  2012 /bin/ksh -> bash
lrwxrwxrwx. 1 root root      4 Feb 29  2012 /bin/sh -> bash
-rwxr-xr-x. 1 root root 380392 Jun 21  2010 /bin/tcsh

Moon5.6 (/dev/pts/2) > unset JPR

Moon5.6 (/dev/pts/2) > JPR=test echo $JPR


Moon5.6 (/dev/pts/2) > echo $JPR


Moon5.6 (/dev/pts/2) >
==========

Ah...  A "man sh" on a SCO box reveals this tidbit, not seen on other systems:

>    The environment for any simple-command may be augmented by prefixing
>    it with one or more assignments to parameters. Thus:
>    TERM=450 cmd
>
>    and
>    (export TERM; TERM=450; cmd)
>
>    are equivalent as far as the execution of cmd is concerned if cmd is
>    not a ``special command'' (see ``Special commands''). If cmd is a
>    special command, then
>    TERM=450 cmd
>
>    will modify the TERM variable in the current shell.



-- 
Kenneth Brody