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我正在尝试在我使用运行的 Linux 命令的输出上运行一些正则表达式exec()。将输出作为干草堆插入时preg_match返回，但是当我将此输出的相同副本放入字符串中并将其用作干草堆时，工作正常并输出预期的数组。NULLexec()preg_match

代码：

exec("/usr/local/bin/ffmpeg -i video.flv 2>&1 | grep Duration", $output);
//$output[0] will be: "Duration: 00:01:00.08, start: 0.042000, bitrate: 164 kb/s"    
$string = $output[0];    
//This regex is to extract the duration, "00:01:00", from the output.
$pattern = "/(^Duration:) ([^&]+)(.[0-9][0-9])(, start)/";    
preg_match($pattern, $string, $matches);
print_r($matches[2]);
//The result should be "00:01:00" but the whole $matches array is empty instead.

//If I added the result of output[0] manually into a string it works fine.
$str = "Duration: 00:01:00.08, start: 0.042000, bitrate: 164 kb/s";
preg_match($pattern, $str, $matches_);
print_r($matches_[2]);
//Outputs "00:01:00" and everything is working fine.

//Just to make sure, I printed $str and $string to see if there is any difference
echo $str."\n".$string;
//The output is:
//Duration: 00:01:00.08, start: 0.042000, bitrate: 164 kb/s
//Duration: 00:01:00.08, start: 0.042000, bitrate: 164 kb/s
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1 回答 1

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使用以下 echo 命令，使用单引号分隔字符串：

echo "'$str'\n'$string'";

输出：

'Duration: 00:01:00.08, start: 0.042000, bitrate: 164 kb/s'
'  Duration: 00:01:12.66, start: 0.000000, bitrate: 127 kb/s'

你看，它们不一样。ffmpeg 在字符串前面添加空格。

但是，如果您将模式更改为：

$pattern = "/(Duration:) ([^&]+)(.[0-9][0-9])(, start)/";

请注意，我已经放弃了^前面的Duration. 现在模式匹配了，尽管字符串前面有一些空格。

于 2013-04-13T19:49:33.090 回答