perl - 如何在 Perl 中解决此警告

Question

我问过这类问题 previously但没有提供完整的代码。

我正在阅读下面的文件并检查每列中存在的最大字宽，然后以适当的对齐方式将其写入另一个文件。

id0 id1 id2 batch
0   34  56  70
2   3647    58  72  566
4   39  616 75  98  78 78987 9876 7899 776
89  40  62  76
8   42  64  78
34  455 544 565

我的代码:

unlink "temp1.log";
use warnings;
use strict;
use feature 'say';
my $log1_file = "log1.log";
my $temp1 = "temp1.log";
open(IN1, "<$log1_file" ) or die "Could not open file $log1_file: $!";
my @col_lens;

while (my $line = <IN1>) {
    my @fs = split " ", $line;
    my @rows = @fs ;
    @col_lens =  map (length, @rows) if $.==1;
    for my $col_idx (0..$#rows) {
        my $col_len = length $rows[$col_idx];
        if ($col_lens[$col_idx] < $col_len) {
            $col_lens[$col_idx] = $col_len;
        }
    };
};
close IN1;
open(IN1, "<$log1_file" ) or die "Could not open file $log1_file: $!";
open(tempp1,"+>>$temp1") or die "Could not open file $temp1: $!";
while (my $line = <IN1>) {
    my @fs = split " ", $line;
    my @az;
    for my $h (0..$#fs) { 
        my $len = length $fs[$h]; 
        my $blk_len = $col_lens[$h]+1;
        my $right = $blk_len - $len;
        $az[$h] = (" ") . $fs[$h] . ( " " x $right );
    }
    say tempp1 (join "|",@az);
};

我的警告

Use of uninitialized value in numeric lt (<) at new.pl line 25, <IN1> line 3.
Use of uninitialized value in numeric lt (<) at new.pl line 25, <IN1> line 4.
Use of uninitialized value in numeric lt (<) at new.pl line 25, <IN1> line 4.
Use of uninitialized value in numeric lt (<) at new.pl line 25, <IN1> line 4.
Use of uninitialized value in numeric lt (<) at new.pl line 25, <IN1> line 4.
Use of uninitialized value in numeric lt (<) at new.pl line 25, <IN1> line 4.

我正在正确获取输出，但不知道如何删除此警告。

Answer 1

$col_idx 最多可以是一行中的字段数减一。对于第三行，这超过了@col_lens的最高索引，它最多包含3个元素。所以做以下是没有意义的:

if ($col_lens[$col_idx] < $col_len) {
   $col_lens[$col_idx] = $col_len;
}

替换为

if (!defined($col_lens[$col_idx]) || $col_lens[$col_idx] < $col_len) {
   $col_lens[$col_idx] = $col_len;
}

有了这个，检查 $ 就真的没有意义了。 == 1 了。