命令行后脚本不继续

Question

我的命令行脚本有问题。PHP 脚本永远不会继续。

尝试通过 putty 直接调用命令行，它会输出很多错误，但会立即返回/完成。为什么不返回 PHP 呢？

它适用于其他 PDF 文件，但不是这个

pdf

http://docdro.id/b0M5vfw

代码

$Cmd = new Command;
if($err = $Cmd->exec('/var/bin/poppler-0.51.0/utils/pdfimages -list /var/test.pdf')){
    echo "ERR: $err\n";
}
echo "continue\n";

类

class Command {
    private $descriptorspec;

    private $output = '';

    private $process;
    private $pipes = [];

    public function __construct(){
        $this->descriptorspec = [
            0 => ['pipe', 'r'], // stdin
            1 => ['pipe', 'w'], // stdout
            2 => ['pipe', 'w']  // stderr
        ];
    }

    public function output(): string{
        return $this->output;
    }

    public function close(){
        foreach($this->pipes as $pipe){
            if(is_resource($pipe)){
                fclose($pipe);
            }
        }

        proc_close($this->process);
    }

    public function exec(string $syntax){
        $this->process = proc_open($syntax, $this->descriptorspec, $this->pipes);
        fclose($this->pipes[0]);

        $this->output = stream_get_contents($this->pipes[1]);

        $stderr = stream_get_contents($this->pipes[2]);

        $this->close();

        return $stderr;
    }
}

错误

# /var/bin/poppler-0.51.0/utils/pdfimages -list /var/test.pdf
page   num  type   width height color comp bpc  enc interp  object ID x-ppi y-ppi size ratio
--------------------------------------------------------------------------------------------
   1     0 image    2154   303  rgb     3   8  jpeg   yes  [inline]     289   292    -    -
Syntax Error (50560): Illegal character '>'
Syntax Error (50560): Unknown operator '<10><07><82>;w<ad><a2><b4>2r<1f><10><07><8f>~j<c4>Hq<cf>Z<86>'
Syntax Error (50568): Unknown operator '<0f><b5>X<8f><ae><d0>:<d7>DU<91><cb>'v'
Syntax Error (50568): Illegal character ')'

........

Syntax Error (66698): Illegal character <04> in hex string
Syntax Error (66699): Illegal character <ff> in hex string
Syntax Error (66699): Illegal character <c1> in hex string
Syntax Error (66705): Unknown operator '<9b>'
Syntax Error (66714): Illegal character ')'
Syntax Error (66714): Unknown operator '<bc>q<ff>'
Syntax Error (66720): Unknown operator '<05>6<f8><c2><fa><d7><c3>?<f8>'
Syntax Error (66741): Unknown operator '<df><ec><99><e1>-'
Syntax Error (66743): Unknown operator ']'
Syntax Error (66762): Unknown operator '<cc>'
Syntax Error: Unterminated string
Syntax Error: End of file inside array
Syntax Error: End of file inside array
Syntax Error: Leftover args in content stream

Answer 1

问题是这个程序/var/bin/poppler-0.51.0/utils/pdfimages 没有写任何东西到stdout 并且你的代码挂在$this->output = stream_get_contents($this->pipes[1]); 因此你的类不适合这个程序。对于不向stdout 写入任何内容的程序，您不得从$this->pipes[1] 中读取。您应该有另一个用于这种特定类型应用程序的类：

class CommandWithNoOutput {
    private $descriptorspec;

    private $process;
    private $pipes = [];
    private $output = '';

    public function __construct(){
        $this->descriptorspec = [
            0 => ['pipe', 'r'], // stdin
            1 => ['pipe', 'w'], // stdout
            2 => ['pipe', 'w']  // stderr
        ];
    }

    public function output(): string{
        return (string)$this->output;
    }


    public function close(){
        foreach($this->pipes as $pipe){
            if(is_resource($pipe)){
                fclose($pipe);
            }
        }

        proc_close($this->process);
    }

    public function exec($syntax){

        $this->process = proc_open($syntax, $this->descriptorspec, $this->pipes);
        fclose($this->pipes[0]);

        $stderr = stream_get_contents($this->pipes[2]);

        $this->close();

        $this->output = ob_get_clean();

        return $stderr;
    }
}

$Cmd = new CommandWithNoOutput;
if($err = $Cmd->exec('/usr/bin/pdfimages -list test.pdf')){
    echo "ERR: $err\n";
}
echo "continue\n";

这段代码输出如下：

ERR: Syntax Error (50560): Illegal character '>'
Syntax Error (50560): Unknown operator '<10><07><82>;w<ad><a2><b4>2r<1f><10><07><8f>~j<c4>Hq<cf>Z<86>'
Syntax Error (50568): Unknown operator '<0f><b5>X<8f><ae><d0>:<d7>DU<91><cb>'v'
Syntax Error (50568): Illegal character ')'
Syntax Error (50570): Unknown operator '<15><c7>=j<c4>X<f4><e8>'
.....a lot of errors.....
Syntax Error (66762): Unknown operator '<cc>'
Syntax Error: Unterminated string
Syntax Error: End of file inside array
Syntax Error: End of file inside array
Syntax Error: Leftover args in content stream

continue

Process finished with exit code 0

更新： 另一种解决方案是在调用proc_open 之后立即调用stream_set_blocking($this->pipes[1], 0);，这样代码就不会等待任何输出。

Answer 2

您可以将stream_select 与feof 结合使用来检查两个读取流中的哪一个具有可用数据，如以下代码。

我已经对其进行了测试（使用 PHP 7）并且它不会在此处阻塞（进行了修改）。

    public function exec(string $syntax){
        $this->process = proc_open($syntax, $this->descriptorspec, $this->pipes);
        fclose($this->pipes[0]);

        $stderr = "";

        $num_changed_streams = NULL;
        while (!feof($this->pipes[1]) || !feof($this->pipes[2])) {
          $read = [$this->pipes[1], $this->pipes[2]];
          $write = NULL;
          $err = NULL;
          $num_changed_streams = stream_select($read, $write, $err, 3);
          if ($num_changed_streams === false) {
            $this->close();
            return $stderr;
          } else {
            if (isset($read[0])) {
              $this->output .= stream_get_contents($read[0]);
              echo "output: {$this->output} ";
            }
            if (isset($read[1])) {
              $stderr .= stream_get_contents($read[1]);
              echo "stderr: {$stderr}";
            }
          }
        }
        $this->close();
        return $stderr;
    }

需要stream_select 和feof 函数，原因如下（引用自http://php.net/manual/en/function.stream-select.php）：

将监视读取数组中列出的流，以查看字符是否可用于读取（更准确地说，查看读取是否不会阻塞 - 特别是，流资源在文件结束时也已准备好，在这种情况下， fread() 将返回一个长度为零的字符串）。

Answer 3

PDF 有问题 - @dwarring 在 cmets 中已经避开了这一点（在此引用以感谢评论者）

@dwarring 说：“很快，我很确定这个 PDF 即将死去，因为内容流包含一个内联图像，以 'BI' 开头，后跟随机数据，以 'EI' 结尾。Adobe 工程师正在当他们设计这些运算符时，问题是出现二进制数据随机包含“EI”并使PDF无法解析的情况。一些工具可能会更好地处理这个问题，但理想情况下，该图像的制作者应该避免使用内嵌图片。”

不过，从 PHP 方面来说，使用 try/catch 块代替 if 语句，您应该保留对脚本的控制权。

$Cmd = new Command;

try {
    $err = $Cmd->exec('/var/bin/poppler-0.51.0/utils/pdfimages - list/var/test.pdf')){
} catch (Exception $e) {
    var_log($e);
}

echo "continue\n";