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Re: Using environmnet variables in make

From: Paul Smith
Subject: Re: Using environmnet variables in make
Date: Sat, 28 Feb 2009 17:42:46 -0500

On Sat, 2009-02-28 at 17:04 -0500, David Boyce wrote:
> On Sat, Feb 28, 2009 at 4:51 PM, Paul Smith <address@hidden> wrote:
>         In this example you actually don't even need to export
>         QA_STEP, since
>         only the shell is expanding it.  But, if you do really need to
>         export it
>         then please do it portably:
>                test:
>                        @QA_STEP=start; export QA_STEP; <do-something>

> Since we're into pet peeves, and since as you note make uses /bin/sh,
> why not push
> test:
>         @QA_STEP=start <do-something>
> as the recommended "elegant" option? It's worked on every /bin/sh ever
> made and it's the way one-shot exporting was originally designed to
> work.

In the original situation: export FOO=bar; touch $FOO
changing it to: FOO=bar touch $FOO
won't work since $FOO is expanded before FOO is assigned.

You're absolutely right, of course; in the case quoted above it's better
to do it your way, _but_ IFF <do-something> is a single command.  If
it's a longer script where QA_STEP is needed in multiple commands, you'd
need to export separately still.

Anyway, I wasn't trying to give a master class in shell programming best
practices, I just wanted to get rid of obvious non-portabilities :-)

 Paul D. Smith <address@hidden>          Find some GNU make tips at:            
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist

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