使用Chart模块时，删除未定义值的警告

Question

我使用图表模块从CSV数据生成PNG格式的图表：

效果很好，图表看起来还不错，但我收到了undef值的警告（上图中末尾有3个这样的值）：

#  ~/txv3.pl "./L*TXV3*.csv"  > /var/www/html/x.html
Generating chart: L_B17_C0_TXV3LIN_PA3_TI1_CI1
Use of uninitialized value $label in length at /usr/share/perl5/vendor_perl/Chart/Base.pm line 3477, <> line 69.
Use of uninitialized value in subroutine entry at /usr/share/perl5/vendor_perl/Chart/Base.pm line 3478, <> line 69.
Use of uninitialized value $label in length at /usr/share/perl5/vendor_perl/Chart/Base.pm line 3477, <> line 69.
Use of uninitialized value in subroutine entry at /usr/share/perl5/vendor_perl/Chart/Base.pm line 3478, <> line 69.
Use of uninitialized value $label in length at /usr/share/perl5/vendor_perl/Chart/Base.pm line 3477, <> line 69.
Use of uninitialized value in subroutine entry at /usr/share/perl5/vendor_perl/Chart/Base.pm line 3478, <> line 69.

我需要摆脱这些警告，因为它们在这里没用，它们使我的Hudson工作日志变得难以理解。

所以我尝试过（在CentOS 6.4 / 64位上使用perl 5.10.1）：

#!/usr/bin/perl -w
use strict;
....

$pwrPng->set(%pwrOptions);
$biasPng->set(%biasOptions);

my $pwrPngFile = File::Spec->catfile(PNG_DIR, "${csv}_PWR.png");
my $biasPngFile = File::Spec->catfile(PNG_DIR, "${csv}_BIAS.png");

{
        no warnings;

        $pwrPng->png($pwrPngFile, $pwrData);
        $biasPng->png($biasPngFile, $biasData);
}

但警告仍然打印出来。

有什么建议吗？

Answer 1

通常最好不要忽略警告。

为什么不在绘制图表之前先处理undef值？ 要么用合理的东西替换它们，要么跳过绘制那些行：

data.csv

RGI,BIAS,LABEL
20,130,"1146346307 #20"
21,135,"1146346307 #21"
22,140,

-

use Scalar::Util qw( looks_like_number );
my $fname = "data.csv";
open $fh, "<$fname"
   or die "Unable to open $fname : $!";

my $data = [];
while (<$fh>) {
   chomp;
   my ($rgi, $bias, $label) = split /,/;   # Better to use Text::CSV
   next unless looks_like_number($rgi);
   next unless looks_like_number($bias);
   $label ||= "Unknown Row $."; # Rownum

   # Create whatever structure you need.
   push @$data, { rgi => $rgi, bias => $bias, label => $label };
}

# Now draw chart

Answer 2

在你的Hudson作业中，为warn信号安装一个处理程序，用于过滤警告，以便你知道的那些不会出现。

BEGIN { 
    $SIG{'__WARN__'} = sub { my $w = shift; warn $w if $w !~ m|/Chart/Base.pm| };
}