Xiecheng shell_ How to capture standard error stream in Exec


Today inGitHubI saw a very interesting question from foreign friends on the homepageissueHe’s using itCo\System::exec()When a non-existent command is executed, the error message will be printed directly to the screen instead of returning the error message.

actuallySwooleProvidedSystem::exec()Behavior andPHPOfshell_execIt’s exactly the same. Let’s write oneshell_execAfter execution, it is found that the output of standard error stream is not available, and it will be printed directly to the screen.

$result = shell_exec('unknown');
[email protected]:~/workspace/debug$ php s.php
sh: 1: unknown: not found
[email protected]:~/workspace/debug$

So how to solve this problem? The answer is to useproc_open+hookrealization.

Instance code

Swoole\Coroutine\run(function () {
    $descriptorspec = array(
        0 => array("pipe", "r"),
        1 => array("pipe", "w"),
        2 => array("pipe", "w"),

    $process = proc_open('unknown', $descriptorspec, $pipes);

    var_dump(fread($pipes[2], 8192));
    $return_value = proc_close($process);

    echo "command returned $return_value\n";

useproc_open, introduced3Description information:

  • fdby0The stream of is the standard input. You can write data to the stream in the main process, and the child process can get the data
  • fdby1The stream of is the standard output, where you can get the output content of executing the command
  • fdby2Ofpipe streamnamelystderr, readstderrYou can get the error message output

usefreadYou can get the output of the standard error stream.

[email protected]:~/workspace/swoole/examples/coroutine$ php proc_open.php
array(3) {
  resource(4) of type (stream)
  resource(5) of type (stream)
  resource(6) of type (stream)
string(26) "sh: 1: unknown: not found
command returned 32512
[email protected]:~/workspace/swoole/examples/coroutine$

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Xiecheng shell_ How to capture standard error stream in Exec

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