perl - 获取哈希的哈希键

Question

我正在尝试获取哈希的哈希键并且总是有错误：

use strict;

my %oop_hash = ();
$oop_hash{'wfh'}{'ppb'} = "451103";
print (keys $oop_hash{'wfh'})."\n"; #1st try
print (keys %oop_hash{'wfh'})."\n"; #2nd try

如何获取哈希的哈希键？

Answer 1

这有点棘手。正确的语法是

keys %{$oop_hash{'wfh'}}

此外，正如您编写的那样，您的print 语句不会完全按照您的意愿行事。由于"\n"Perl 解析该行的方式，不会将其附加到字符串中。您必须说以下之一：

print +(keys %{$oop_hash{'wfh'}}),"\n"; 
print ((keys %{$oop_hash{'wfh'}}),"\n");

Answer 2

这里是：

#!/usr/bin/perl
use strict;
use warnings;

my %oop_hash = ();
$oop_hash{'wfh'}{'ppb'} = "451103";
print join ", ", keys $oop_hash{'wfh'} , "\n"; # "ppb, "