获取哈希哈希的密钥

Question

我正在尝试获取哈希散列的键并始终有错误：

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

如何获取哈希哈希的键？

Answer 1

这有点棘手。正确的语法是

keys %{$oop_hash{'wfh'}}

另外，正如您所写，print statement will not quite do what you want。由于Perl解析该行的方式，"\n"不会附加到字符串。你不得不说：

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, "