passing data to variable in if statment

stuffy has asked for the wisdom of the Perl Monks concerning the following question:

It's been a long time since I tried programming, and I'm having some problems. $gust is declared earlier and passed a value from geo::METAR. If there is no wind gust, then no value is passed. I check to see if it's nul, it if is, I want to do something, if it has a value I want to do something else. I'm getting a Use of uninitialized value in concatenation (.) or string at.... error when trying to call $gusting when $gust has no value. It seems like I'm missing something simple here!

my $wind = $m->WIND_MPH;
my $w_dir = $m->WIND_DIR_ENG;
my $gust = $m->WIND_GUST_MPH;
my $gusting;

    if ($gust eq "")  {
        $gusting ="not gusting";
    }
    else {
        $gusting ="gusting to $gust";
    }
print "$gusting";
[download]

Stuffy
That's my story, and I'm sticking to it, unless I'm wrong in which case I will probably change it ;~)
may be reproduced under the SDL

Comment on passing data to variable in if statment Download Code

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Re: passing data to variable in if statment by FunkyMonk (Bishop) on May 06, 2008 at 21:02 UTC
Are you sure WIND_GUST_MPH contains the empty string and not undef? In either case, you can use `if ($gust) { $gusting ="gusting to $gust"; } else { $gusting ="not gusting"; }` [download] Unless I state otherwise, all my code runs with strict and warnings	[reply] [d/l] [select]
Re^2: passing data to variable in if statment by stuffy (Monk) on May 06, 2008 at 21:13 UTC
You are correct, it is not an empty string. Your fix did the trick. I thought about switching it around, but I thought that what I had was correct, and would have been if an empty string was being passed. Thank you for your help. Stuffy That's my story, and I'm sticking to it, unless I'm wrong in which case I will probably change it ;~) may be reproduced under the SDL	[reply]
Re^3: passing data to variable in if statment by GrandFather (Saint) on May 07, 2008 at 00:53 UTC
On a related note you may be interested in True or False? A Quick Reference Guide. Perl is environmentally friendly - it saves trees	[reply]
Re: passing data to variable in if statment by Paladin (Vicar) on May 06, 2008 at 21:00 UTC
Use `defined $var` to see if a variable is defined or not. `""` is different from `undef`	[reply] [d/l] [select]