On Fri, 2005-02-11 at 12:48 -0700, der.hans wrote:
> Am 11. Feb, 2005 schwätzte Ben Weatherall so:
>
> > Sorry for having to reply from a Gates-based system, it is all I have
> > access to at work)...
>
> Well, upgrade $ENV{ 'WORK' } ;-).
>
> > Remember that perl has a nasty feature of automatically instantiating
> > any hash entry referenced in a test. In other words, if( $ENV{
> > 'USERADMIN_USER' } ) { will cause the USERADMIN_USER entry in the %ENV
> > hash to come into being with a null or undefined value, even if it did
> > NOT exist prior to the test. In some perl's even the following does not
> > keep it from being instantiated, if ( defined($ENV{ 'USERADMIN_USER' } )
> > && $ENV{ 'USERADMIN_USER' } ) {
>
> You're talking about auto-vivification ( man pages are nice ), but that
> shouldn't affect if() as undef still evaluates to false for if().
>
> You are correct, though, that using defined() is a better practice.
>
> defined() will also auto-vivify.
>
> lufthans@dth:~$ perl -e 'if( $ENV{ 'FRED' } ) { print "fred\n"; } else {
> print "nope\n" } if( $ENV{ 'FRED' } ) { print "anke\n"; } else { print
> "nope\n"; } if( $ENV{ 'FRED' } ) { print "udo\n"; } else { print "nope\n";
> }'
> nope
> nope
> nope
> lufthans@dth:~$ perl -e 'if( $ENV{ 'FRED' } ) { print "fred\n"; } else {
> print "nope\n" } if( exists( $ENV{ 'FRED' } ) ) { print "anke\n"; } else {
> print "nope\n"; } if( defined( $ENV{ 'FRED' } ) ) { print "udo\n"; } else
> { print "nope\n"; }'
> nope
> nope
> nope
> lufthans@dth:~$ perl -e 'if( $ENV{ 'FRED' } ) { print "fred\n"; } else {
> print "nope\n" } if( defined( $ENV{ 'FRED' } ) ) { print "anke\n"; } else
> { print "nope\n"; } if( exists( $ENV{ 'FRED' } ) ) { print "udo\n"; } else
> { print "nope\n"; }'
> nope
> nope
> nope
----
somewhere in this there may be the answer and given the beauty of perl
code, I can't decipher most of it...
I know with a shell script, I can insert a command like...
/bin/env > /tmp/env.txt
to dump my current variable list to a file. It would truly help my
debugging of perl if I knew how to do the same thing in perl.
Thanks
Craig
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