php exec usage

In PHP, the exec function can be used to execute a system command. Its basic syntax is as follows:

string exec ( string $command [, array &$output [, int &$status ]] )

Among them, $command is the system command to be executed; $output is an array used to store the output results after command execution; $status is an integer used to store the command execution status.

Example:

$cmd = 'ls -l';
exec($cmd, $output, $status);
print_r($output);
echo $status;

The above code executes an ls command, stores the results in the $output array, and outputs the $status value.

The exec function does not return the output results of command execution, but stores the results in the $output variable. If the command has no output, the $output array is empty.

If you want to return the output of command execution, you can use the `` symbol or the shell_exec function.

Example:

$cmd = 'echo "hello world"';
$output = `$cmd`;
echo $output;

The above code executes an echo command and outputs the results to the screen.

It should be noted that the exec function needs to pay attention to security issues when executing commands. If the $command parameter is obtained via user input, the input should be sanitized to avoid security issues such as command injection.

In addition, the exec function may be limited by the system environment, and may behave differently on different systems. Therefore, when using the exec function, you need to carefully review the command and its output and follow best practices to avoid potential problems.

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