如何确保一次只运行一个Perl脚本副本? [英] How can I ensure only one copy of a Perl script is running at a time?

问题描述

我需要确保一次只运行我的Perl脚本的一个副本.根据此处的建议，我写了一个子代码进行检查:

I need to ensure that only one copy of my Perl script is running at a time. According to the suggestions here I wrote a sub to do the check:

sub check_instances {
    open my $fh, '<', $0 or die $!; 

    unless (flock($fh, LOCK_EX|LOCK_NB)) {
        print "$0 is already running. Exiting.\n";
        exit 1;
    } 
}

但是它不起作用.可能是什么问题?

But it doesn't work. What can be the issue?

推荐答案

您正在使用范围在子对象内的词法文件句柄.当返回check_instances时，文件句柄将自动关闭，从而释放锁定.因此，除非有两个副本完全同时检查，否则您永远不会看到冲突.

You're using a lexical filehandle scoped inside the sub. When check_instances returns, the filehandle is automatically closed, which releases the lock. So you'll never see a conflict unless two copies check at exactly the same time.

确保只要脚本正在运行(或者只要您想保持锁定)，文件句柄就保持打开状态.例如:

Ensure that the filehandle remains open as long as the script is running (or as long as you want to maintain the lock). For example:

{
my $fh;
sub check_instances {
    return if $fh; # We already checked
    open $fh, '<', $0 or die $!; 

    unless (flock($fh, LOCK_EX|LOCK_NB)) {
        print "$0 is already running. Exiting.\n";
        exit 1;
    } 
}
} # end scope of $fh

如果使用 state变量，这也是一个好地方.您可以要求使用Perl 5.10.

This would also be a good place to use a state variable, if you can require Perl 5.10.

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