Re: Silly shell question

[Johnny Billquist <bqt%update.uu.se@localhost>]

It's simpler than that. KSH (along with SH, BASH and similar shells) 
have two sets of variables. Local and environment. A variable can only 
exist in one of these. By default, when a variable is created, it is 
local. If you export it, it becomes an environment variable.

Only environment variables are propagated to child processes.

(In shells from the csh family, you have different commands for dealing 
with local and environment variables, so there it is a bit more obvious 
what you are doing.)

	Johnny

On 2016-03-22 21:39, Swift Griggs wrote:
> In ksh, when you use the 'export' keyword, what is actually going on?
> Does it create a copy of the variable in memory? I doubt it since I
> tried a test and I could see the exported version changing even if I
> just change the original variable:
>
> # FOO=abc
> # export FOO
> # ksh
> # echo $FOO
> abc
> # exit
> # FOO=123
> # ksh
> # echo $FOO
> 123
> # exit
>
> So, what is that really happens with exported variables? Does the
> shell/app that's starting up check for exported variables and somehow
> import them? How can it tell? I noticed there are a LOT of checks around
> exported variables in ast-ksh. It appears to be a dangerous proposition
> in some cases.
>
> Sorry if this seems like a dumb question. I'm just curious about the
> intrinsics of how it works. I looked at the source code for ast-ksh, but
> it's pretty huge and hard to follow to answer this question. I'm just
> wondering what the key mechanism is. Curiosity only.
>
> -Swift


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Johnny Billquist                  || "I'm on a bus
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