从Perl的文件栏获取唯一值 [英] Perl getting unique values from file column

问题描述

我有一个具有以下数据的文件：

i have a file that has the following data:

col1 col2 ext3 rw
col1 col2 ext3 rw 
col1 col2 ext3 rw 
col1 col2 nfs rw 
col1 col2 ext4 rw 
col1 col2 iso9660 ro

什么我试图做的是阅读文件，并从第3列列3包含ext3的打印独特的价值观，EXT4，NFS ...

what am trying to do is to read the file and print unique values from column 3. The column 3 contains the ext3,ext4,nfs ...

目前我的输出是：

ext3 
ext3 
ext3 
nfs 
ext4 
iso9660

和我的输出应该是：

ext3
nfs
ext4
iso9660

下面是我曾尝试到现在：

Below is what i have tried till now:

#!/usr/bin/perl    
use strict;
use warnings; 
my $filename = $ARGV[0];
open(FILE, $filename) or die "Could not open file '$filename' $!";
while (<FILE>)
{
    chomp;
    my $line = $_;
    my @elements = split (" ", $line);
    my $row_name = $elements[2];
    print $row_name . "\n";

}
close FILE;

我如何将其打印在同一程序中的独特价值？
谢谢你。

How do i make it print the unique values in the same program? Thank you.

推荐答案

使用一个Perl oneliner

Using a perl oneliner

perl -lane 'print $F[2] if ! $seen{$F[2]}++' file.txt

或者你的脚本中，加入了％看过哈希值表现在<一个href=\"http://perldoc.perl.org/perlfaq4.html#How-can-I-remove-duplicate-elements-from-a-list-or-array%3f\"相对=nofollow> perlfaq4如何删除从列表或数组重复的元素？

Or within your script, by adding a %seen hash as demonstrated in perlfaq4 How can I remove duplicate elements from a list or array?

use strict;
use warnings; 
my $filename = $ARGV[0];
open(FILE, $filename) or die "Could not open file '$filename' $!";
my %seen;
while (<FILE>)
{
    chomp;
    my $line = $_;
    my @elements = split (" ", $line);
    my $row_name = $elements[2];
    print $row_name . "\n" if ! $seen{$row_name}++;
}
close FILE;

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