如何结合popen和file_get_contents从命令输出中读取数据？

在PHP中处理外部命令并读取其输出通常有多种方式，例如使用exec、shell_exec、popen等函数。其中，popen提供了一种面向流的方式来读取命令行工具的输出，这种方式在处理持续输出或需要分段读取的场景下尤其实用。

此外，file_get_contents通常用于读取文件或URL内容，但你可能不知道，它同样可以用来读取通过popen创建的流。本文将介绍如何结合这两个函数，从命令的输出中高效读取数据。

一、popen 简介

popen的函数原型如下：

resource popen(string $command, string $mode)

它用于执行一个命令，并打开一个可以读取或写入的文件指针。$mode可以是'r'（读取）或'w'（写入），不过我们这里关注的是读取模式。

二、file_get_contents 读取流

通常我们使用file_get_contents来读取静态文件或者像 http://m66.net/data.json 这样的远程资源。但由于file_get_contents支持读取任何流资源，它也可以用于读取通过popen打开的命令输出。

三、示例：读取 ls 命令输出

下面是一个实际示例，我们将执行ls命令，并读取其输出内容：

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$cmd = 'ls -la'; // 你可以替换成任何你想执行的命令
$handle = popen($cmd, 'r');

if (is_resource($handle)) {
    $output = stream_get_contents($handle);
    pclose($handle);
    echo "<pre>$output