Use of uninitialized value in numeric gt (>)

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

Hi Monks, I have searched for this and found several nodes but could not find any that appeard to answer my question.. so I pose it here:

I want to check the length of a file to determing the value of a variable for later use.

my $offline = 1 if (-s 'online.flg' gt 0);
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This gets a warning Use of uninitialized value in numeric gt (>) so systematically I try defining each of the 3 elements:

my $flag_size = -s 'online.flg';
my $offline = 1 if ($flag_size > 0);
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my $flag_size = -s 'online.flg';
my $zero_value = 0;
my $offline = 1 if ($flag_size > $zero_value);
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I even tried re-aranging my if statement:

my $zero_value = 0;
my $flag_size  = -s 'online.flg';
my $offline = 0;
if($flag_size > $zero_value){
  $offline = 1;
}
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All of them get the same warning.. can anyone shed any light on this?

Thanks,

 ___
/\__\ "What is the world coming to?"
\/__/ www.wolispace.com
[download]

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Re: Use of uninitialized value in numeric gt (>) by Aristotle (Chancellor) on Aug 12, 2004 at 02:23 UTC
First of all: don't do `my $foo if $cond;` — that's going to surprise you when the condition is false, because my has both compile-time and runtime implications, but the conditional is suppressing the runtime effect. In this particular case, you don't need an `if` either — a condition returns a boolean value. So you can just say `my $offline = ( -s 'online.flg' ) > 0;` [download] and later do something like `if( $offline )` just fine. Actually, you don't even need to have the comparison, because if -s returns 0, that's false, and if it returns a value greater than zero, that is interpreted as true. You could just say `my $offline = -s 'online.flg';` [download] and using `$offline` as a boolean would do the right thing. Finally, all that said and done — I can't reproduce your problem with an existing file. -s returns undef for non-existent ones, though. Is that the source of your problem? Makeshifts last the longest.	[reply] [d/l] [select]
Re^2: Use of uninitialized value in numeric gt (>) by hv (Prior) on Aug 12, 2004 at 11:49 UTC
Finally, all that said and done — I can't reproduce your problem ... Not surprising: the OP's warning specifically says `numeric gt (>)`, not `string gt`. I suspect that the warning is coming from a different line of code. Hugo	[reply] [d/l] [select]
Re: Use of uninitialized value in numeric gt (>) by Zaxo (Archbishop) on Aug 12, 2004 at 02:19 UTC
Does the file exist with that relative path from where the script runs? You can test that at runtime with -f. You may want to give an absolute path so that you can run from anywhere. After Compline, Zaxo	[reply]
Re: Use of uninitialized value in numeric gt (>) by YuckFoo (Abbot) on Aug 12, 2004 at 22:54 UTC
The problem is -s returns undef if the file does not exist. Then undef causes the 'uninitialized' warning. One fix for this is to set $flag_size to 0 when -s returns undef: `my $flag_size = -s 'online.flg' \|\| 0;` [download] YuckDef	[reply] [d/l]
Re^2: Use of uninitialized value in numeric gt (>) by wolis (Scribe) on Aug 13, 2004 at 07:19 UTC
Thankyou, and everyone who replied. I will now go and check but I recon your right. The file did not exist. I will check out -f as all I really want to do is know if a file exists I dont really care what size it is if it does exist. Ideally Id like to do this: `my $offline = -f 'online.flg';` [download] ..with the hope that it will return false if the file doesn't exist (without raising a warning) - thus achieving my aim. Thanks Monks! `___ /\__\ "What is the world coming to?" \/__/ www.wolispace.com` [download]	[reply] [d/l] [select]