在 Perl-Tk 中使用 Button 小部件执行命令
#!/usr/local/bin/perl
use Tk;
# Main Window
$mw = new MainWindow;
$label = $mw -> Label(-text=>"Hello World") -> pack();
$button = $mw -> Button(-text => "Quit",
-command => sub { exit }) -> pack();
MainLoop;
在此代码中，当按下按钮 $button 时，它将关闭程序。因为它执行的是exit命令。我想修改代码，以便当用户单击按钮时它将刷新 iptables 规则（iptables -F）。我该怎么做？
我尝试过：
$button = $mw -> Button(-text => "Flush the rules",
-command => system ( iptables -F )) -> pack();
为什么这不起作用？我是否必须为其创建一个子例程（然后在那里编写 iptables -F 命令）然后调用该子例程？我不能像上面的代码一样直接输入命令吗？
#!/usr/local/bin/perl
use Tk;
# Main Window
$mw = new MainWindow;
$label = $mw -> Label(-text=>"Hello World") -> pack();
$button = $mw -> Button(-text => "Quit",
-command => sub { exit }) -> pack();
MainLoop;
In this code when the button $button is pressed it closes the program. Because it executes the exit command. I want to modify the code so that when the user clicks on the button it will flush the iptables rule (iptables -F). How can I do this?
I tried this:
$button = $mw -> Button(-text => "Flush the rules",
-command => system ( iptables -F )) -> pack();
Why isn't this working? Should I have to make a subroutine for it (then writing the iptables -F command there) and then call that subroutine? Can't I directly put the command as I did in above code?
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您需要指定一个代码引用 - 一个回调 - 将在按下按钮时执行，因此您应该将系统调用放在
sub { }中。您编写的是在定义 Button 时对 system() 的调用，因此您将 system() 的返回值指定为回调的 coderef - 这是行不通的。 system() 函数将在定义 Button 时调用，而不是在按下按钮时调用 - 这不是您想要的。
You need to specify a code reference - a callback - which will be executed when the button is pressed, so yes you should place your system call in a
sub { }.What you've written is a call to system() at the point that the Button is defined, so you're specifying the return value from system() as the coderef for the callback - which won't work. The system() function will be called when Button is defined, not when its pressed - which isn't what you want.