为什么调用此函数会改变我的数组？

Question

每当我读取文件时,Perl似乎都在杀死我的数组:

my @files = ("foo", "bar", "baz");
print "Files: " . join(" ", @files) . "\n";

foreach(@files) {
   print "The file is $_\n";
   func();
}

sub func {
   open(READ, "< test.txt");
   while(<READ>) {
   }
   close READ;
}

print "Files: " . join(" ", @files) . "\n";

生产:

Files: foo bar baz
The file is foo
The file is bar
The file is baz
Files:

但是当我发表评论时func(),它给出了我所期望的:

Files: foo bar baz
The file is foo
The file is bar
The file is baz
Files: foo bar baz

任何想法为什么会这样？

Answer 1

您必须更改foo为本地化$_,或不在$_循环中使用.最好的,做到两个:

foreach my $filename (@files) {
    print "The file is $filename\n";
    func();
}

sub func {
    local $_;
    open my $read, '<', 'test.txt' or die "Couldn't open test.txt: $!";
    while(<$read>) {
    }
    close $read or die "Couldn't close file: $!";
}

foreach循环别名$_为文件的当前名称并while(<READ>)分配给$_.这就是魔术的糟糕组合,可以这么说.

一般来说,除了单线之外,依靠$_其他任何东西都是一个坏主意.