如何从 Perl 中的管道进行非阻塞读取？

发布于 2024-09-24 12:51:48 字数 585 浏览 6 评论 0原文

我有一个程序正在调用另一个程序并处理子程序的输出，即：

my $pid = open($handle, "$commandPath $options |");

现在我尝试了几种不同的方法来从句柄读取而不阻塞，但几乎没有成功。

我发现相关问题：

但他们遇到了以下问题：

ioctl 始终
在 0 字节上使 perl sysread 块崩溃（常见情况）

我不知道如何解决这个问题。

原文

I have a program which is calling another program and processing the child's output, ie:

my $pid = open($handle, "$commandPath $options |");

Now I've tried a couple different ways to read from the handle without blocking with little or no success.

I found related questions:

But they suffer from the problems:

ioctl consistently crashes perl
sysread blocks on 0 bytes (a common occurrence)

I'm not sure how to go about solving this problem.

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最初的梦 2024-10-01 12:51:48

管道在 Windows 上的功能不如在 Unix-y 系统上的功能。您不能对它们使用 4 参数 select，并且默认容量很小。

您最好尝试基于套接字或文件的解决方法。

$pid = fork();
if (defined($pid) && $pid == 0) {
    exit system("$commandPath $options > $someTemporaryFile");
}
open($handle, "<$someTemporaryFile");

现在您还有更多的蠕虫需要处理 - 定期运行 waitpid 来检查后台进程何时停止创建输出，调用 seek $handle,0,1从 $handle 读取后清除 eof 条件，清理临时文件，但它有效。

我已将 Forks::Super 模块写入处理这样的问题（以及许多其他问题）。对于这个问题，你可以像这样使用它

use Forks::Super;
my $pid = fork { cmd => "$commandPath $options", child_fh => "out" };
my $job = Forks::Super::Job::get($pid);
while (!$job->is_complete) {
    @someInputToProcess = $job->read_stdout();
    ... process input ...
    ... optional sleep here so you don't consume CPU waiting for input ...
}
waitpid $pid, 0;
@theLastInputToProcess = $job->read_stdout();

Pipes are not as functional on Windows as they are on Unix-y systems. You can't use the 4-argument select on them and the default capacity is miniscule.

You are better off trying a socket or file based workaround.

$pid = fork();
if (defined($pid) && $pid == 0) {
    exit system("$commandPath $options > $someTemporaryFile");
}
open($handle, "<$someTemporaryFile");

Now you have a couple more cans of worms to deal with -- running waitpid periodically to check when the background process has stopped creating output, calling seek $handle,0,1 to clear the eof condition after you read from $handle, cleaning up the temporary file, but it works.

I have written the Forks::Super module to deal with issues like this (and many others). For this problem you would use it like

use Forks::Super;
my $pid = fork { cmd => "$commandPath $options", child_fh => "out" };
my $job = Forks::Super::Job::get($pid);
while (!$job->is_complete) {
    @someInputToProcess = $job->read_stdout();
    ... process input ...
    ... optional sleep here so you don't consume CPU waiting for input ...
}
waitpid $pid, 0;
@theLastInputToProcess = $job->read_stdout();

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