Run Process with Realtime Output in PHP
When executing processes in PHP, it can be desirable to display their output in real time. This article explores a method for achieving this using the exec() function and a unique configuration of descriptor specifications.
Realtime Output Capture
To capture the output of a process in real time, it's necessary to specify the following descriptor specifications:
$descriptorspec = array(
0 => array("pipe", "r"), // stdin is a pipe that the child will read from
1 => array("pipe", "w"), // stdout is a pipe that the child will write to
2 => array("pipe", "w") // stderr is a pipe that the child will write to
);
This setup redirects stdin, stdout, and stderr to pipes, allowing us to read from stdout in real time using the fgets() function.
Example: Ping with Realtime Output
To demonstrate this method, let's run the ping command with realtime output:
$cmd = "ping 127.0.0.1";
$process = proc_open($cmd, $descriptorspec, $pipes, realpath('./'), array());
echo "<pre class="brush:php;toolbar:false">";
if (is_resource($process)) {
while ($s = fgets($pipes[1])) {
print $s;
flush();
}
}
echo "";
This code will output each line of the ping process as it becomes available, providing a live view of the network traffic.
Process Termination
Terminating processes when a user leaves a web page can be a challenge. In the case of long-running processes like ping, they may continue to run even after the page has been closed.
To address this, one can employ the following techniques:
- Use proc_terminate() to explicitly kill the process when the script exits.
- Use pcntl_signal() to trap the user leaving the page and kill the process accordingly.
- Set a timeout for the process and automatically terminate it after a specified period.
By implementing these methods, developers can ensure that processes started from their PHP scripts are properly handled when a user navigates away from the page.
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