Source

File: wp-admin/includes/file.php

function WP_Filesystem( $args = false, $context = false, $allow_relaxed_file_ownership = false ) { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.FunctionNameInvalid
	global $wp_filesystem;

	require_once ABSPATH . 'wp-admin/includes/class-wp-filesystem-base.php';

	$method = get_filesystem_method( $args, $context, $allow_relaxed_file_ownership );

	if ( ! $method ) {
		return false;
	}

	if ( ! class_exists( "WP_Filesystem_$method" ) ) {

		/**
		 * Filters the path for a specific filesystem method class file.
		 *
		 * @since 2.6.0
		 *
		 * @see get_filesystem_method()
		 *
		 * @param string $path   Path to the specific filesystem method class file.
		 * @param string $method The filesystem method to use.
		 */
		$abstraction_file = apply_filters( 'filesystem_method_file', ABSPATH . 'wp-admin/includes/class-wp-filesystem-' . $method . '.php', $method );

		if ( ! file_exists( $abstraction_file ) ) {
			return;
		}

		require_once $abstraction_file;
	}
	$method = "WP_Filesystem_$method";

	$wp_filesystem = new $method( $args );

	/*
	 * Define the timeouts for the connections. Only available after the constructor is called
	 * to allow for per-transport overriding of the default.
	 */
	if ( ! defined( 'FS_CONNECT_TIMEOUT' ) ) {
		define( 'FS_CONNECT_TIMEOUT', 30 );
	}
	if ( ! defined( 'FS_TIMEOUT' ) ) {
		define( 'FS_TIMEOUT', 30 );
	}

	if ( is_wp_error( $wp_filesystem->errors ) && $wp_filesystem->errors->has_errors() ) {
		return false;
	}

	if ( ! $wp_filesystem->connect() ) {
		return false; // There was an error connecting to the server.
	}

	// Set the permission constants if not already set.
	if ( ! defined( 'FS_CHMOD_DIR' ) ) {
		define( 'FS_CHMOD_DIR', ( fileperms( ABSPATH ) & 0777 | 0755 ) );
	}
	if ( ! defined( 'FS_CHMOD_FILE' ) ) {
		define( 'FS_CHMOD_FILE', ( fileperms( ABSPATH . 'index.php' ) & 0777 | 0644 ) );
	}

	return true;
}