pclose failed

This error usually occurs after calling the popen() function and then failing to use pclose(). This article will explain in detail the causes and solutions for this issue.

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• Resource Not Opened Properly: If popen() returns false or the resource is not initialized properly, calling pclose() will fail.
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• Subprocess Abnormal Termination: If the subprocess crashes or terminates unexpectedly during execution, it can also prevent pclose() from closing properly.
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• Repeated Closing of Resource: Calling pclose() multiple times on the same resource will cause an error, as the resource has already been released.
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• Permission Issues: If the PHP runtime user lacks permission to execute certain system commands, it can also lead to pclose() returning an error.
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1. Check the Return Value of popen(): Before calling pclose(), ensure that popen() returns a valid resource.
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<br>
</span></span><span><span>$handle</span></span><span> = popen('ls -l', 'r');<br>
if (</span><span><span>$handle</span></span><span>) {<br>
while (!feof(</span><span><span>$handle</span></span><span>)) {<br>
echo fgets(</span><span><span>$handle</span></span><span>);<br>
}<br>
pclose(</span><span><span>$handle</span></span><span>);<br>
} else {<br>
echo 'Failed to open resource';<br>
}<br>

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2. Ensure the Subprocess Terminates Properly: You can add output logs to the command or append exit 0 at the end of the command to ensure the subprocess returns a normal exit status.
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3. Avoid Repeatedly Closing Resources: Call pclose() only once for each resource. You can check if the variable is of the resource type before using it:
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<br>
if (is_resource(</span></span><span><span>$handle</span></span><span>)) {<br>
pclose(</span><span><span>$handle</span></span><span>);<br>
}<br>

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4. Check for Permission Issues: Ensure the PHP runtime user has permission to execute commands, or use sudo with a configuration file to allow specific commands.
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5. Use try-catch or Error Control: Although pclose() itself does not throw exceptions, you can use the error control operator @pclose() to avoid interrupting the script.
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The 'pclose failed' error is typically caused by resource issues, subprocess abnormal termination, insufficient permissions, or repeated resource closure. By checking the return value of popen(), ensuring proper subprocess termination, avoiding repeated closure, and configuring permissions, most of these issues can be resolved.

In actual development, developing the habit of checking resource validity, catching exceptions, and logging can significantly reduce the probability of encountering such errors.