如何使用perl从文本文件中选择列

Question

I want to subtract values in one column from another column and add the differences.How do I do this in perl? I am new to perl.Hence I am unable to figure out how to go about it. Kindly help me.

Answer 1

The first thing is to separate the data into columns. In this case, the columns are separated by a space. split(/ /) will return a list of the columns.

To subtract one from the other, its pulling the values out of the the list and subtracting them.

At the end, you add the difference to the running sum and then loop over the data.

#!/usr/bin/perl

use strict;

my $sum = 0;

while(<DATA>) {
    my @vals = split(/ /);
    my $diff = $vals[1] - $vals[0];
    $sum += $diff;
}

print $sum,"\n";

__DATA__
1 3
3 5
5 7

This will print out 6 --- (3 - 1) + (5 - 3) + (7 - 5)

Answer 2

仅供参考，如果您结合使用自动拆分（ -a ），循环（ n ）和命令行程序（ -e ）参数（请参阅perlrun ），则可以将其缩短为单行格式 ，就像awk一样：

perl -ane "$sum += $F[1] - $F[0]; END { print $sum }" filename