Jerry Rocteur wrote:
>
> I'm trying to be a good boy and use strict and warnings ..
Well done!
> The more I do, the more I feel I'm wasting so much time and should
> become productive, my code looks full of 'my', I could understand the
> requirement inside a sub routing but in the main code it gives me the
> willies. My DBI Perl is even more of a headache ;-((
Your problem is more than likely because you're expecting Perl to be
like another language. The usual ones are C and shell script. Perl's
syntax is often quite like C's, and the built-in functions are a fair
match, but unless you're used to declaring variables locally to their
scope of use as in C++ you will end up with a long preamble declaring
everything, which can be less than useful.
> Anyway, enough whining, now I've going through code that is working and
> thought I'd see the big difference if I change it to use warnings and
> strict and this little routing gives me 'Use of uninitialized value in
> pattern match (m//) at ./getopt.pl line 14.'
>
> Line 14 is the while line..
'use warnings' will moan at you if a variable's value is 'undefined'.
It's left this way straight after either
my $var
or
$var = undef
If you define stuff like:
my $var = 0
then you won't get this problem. But don't go around initialising
all variables in their declarations. It's just a warning and is useful
as such, and anyway Perl will let you concatenate or increment an
undefined value. i.e.
my $var;
followed by
$var++;
or
$var .= '>>'
will work fine without any warnings.
> I've tried all sorts of stuff with defined but keep getting syntax
> errors. I've tried perldoc warnings and perldoc perllexwarn .. In any
> case, unless I'm really missing something, I can't see what could be
> problematic with the while statement below, of course this shows my
> ignorance but as I've decided to use warnings and strict, I want to do
> it right..
>
> How would a pedant code the following to avoid this warning.. Your
> answers will help me in the future.
You need to get to understand Perl idioms. I've started by reducing your
indents from 8 chars to 2 because that makes it more visible for me.
> if ($#ARGV >= 0) {
This says 'if the index of the last array element is zero or more'.
You don't mean that, because an array with a single element will
have a last element with an index of zero. Try
if (@ARGV) {
:
}
> while ($_ = $ARGV[0], /^-/) {
>
> shift;
OK, these lines together pull the next argument from @ARGV and
quit the loop unless it begins with a hyphen. The reason you're
getting a warning is that once your 'shift' statement below has
finally emptied the array, $_ = $ARGV[0] will set $_ to 'undef'
so the pattern match is comparing against an undefined value.
This does the same:
foreach (@ARGV) {
last unless /^-/;
except that the parameters are left in @ARGV instead of being
shifted off, and the loop is executed just once for each
element of @ARGV.
> last if /^--$/;
Break out if the element is just two hyphens. That's fine.
> if (/^-d(.*)/) {
> $debug++
> }
Again, that'll do. But unless you need to capture whatever follows
the '-d' then you want just
if (/^-d/) {
$debug++
}
> elsif (/^-v(.*)/) {
> $verbose++
> }
Same here:
elsif (/^-v/) {
$verbose++
}
> else {
> print "$_ unknown option\n";
> Usage;
> }
> }
> }
And the rest's OK. But I'd write it something like this. (Actually I would
probably never write this, but my code depends on the context of the
code and what exactly you need to do with the results :)
foreach (@ARGV) {
next unless /^-/;
last if $_ eq '--';
if ( /^-(d|v)/ ) {
$debug++ if $1 eq 'd';
$verbose++ if $1 eq 'v';
}
else {
print "$_ unknown option\n";
Usage;
}
}
HTH,
Rob
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