Sending the reset password link programatically

So if you want to send the reset password link and you have access to the code base, you can use the following snippet and you can modify it further. Actually this code is a slightly modified version of wp-login.php

/**
 * Handles sending password retrieval email to user.
 *
 * @uses $wpdb WordPress Database object
 * @param string $user_login User Login or Email
 * @return bool true on success false on error
 */
function retrieve_password($user_login) {
    global $wpdb, $current_site;

    if ( empty( $user_login) ) {
        return false;
    } else if ( strpos( $user_login, '@' ) ) {
        $user_data = get_user_by( 'email', trim( $user_login ) );
        if ( empty( $user_data ) )
           return false;
    } else {
        $login = trim($user_login);
        $user_data = get_user_by('login', $login);
    }

    do_action('lostpassword_post');


    if ( !$user_data ) return false;

    // redefining user_login ensures we return the right case in the email
    $user_login = $user_data->user_login;
    $user_email = $user_data->user_email;

    do_action('retreive_password', $user_login);  // Misspelled and deprecated
    do_action('retrieve_password', $user_login);

    $allow = apply_filters('allow_password_reset', true, $user_data->ID);

    if ( ! $allow )
        return false;
    else if ( is_wp_error($allow) )
        return false;

    $key = $wpdb->get_var($wpdb->prepare("SELECT user_activation_key FROM $wpdb->users WHERE user_login = %s", $user_login));
    if ( empty($key) ) {
        // Generate something random for a key...
        $key = wp_generate_password(20, false);
        do_action('retrieve_password_key', $user_login, $key);
        // Now insert the new md5 key into the db
        $wpdb->update($wpdb->users, array('user_activation_key' => $key), array('user_login' => $user_login));
    }
    $message = __('Someone requested that the password be reset for the following account:') . "\r\n\r\n";
    $message .= network_home_url( "https://wordpress.stackexchange.com/" ) . "\r\n\r\n";
    $message .= sprintf(__('Username: %s'), $user_login) . "\r\n\r\n";
    $message .= __('If this was a mistake, just ignore this email and nothing will happen.') . "\r\n\r\n";
    $message .= __('To reset your password, visit the following address:') . "\r\n\r\n";
    $message .= '<' . network_site_url("wp-login.php?action=rp&key=$key&login=" . rawurlencode($user_login), 'login') . ">\r\n";

    if ( is_multisite() )
        $blogname = $GLOBALS['current_site']->site_name;
    else
        // The blogname option is escaped with esc_html on the way into the database in sanitize_option
        // we want to reverse this for the plain text arena of emails.
        $blogname = wp_specialchars_decode(get_option('blogname'), ENT_QUOTES);

    $title = sprintf( __('[%s] Password Reset'), $blogname );

    $title = apply_filters('retrieve_password_title', $title);
    $message = apply_filters('retrieve_password_message', $message, $key);

    if ( $message && !wp_mail($user_email, $title, $message) )
        wp_die( __('The e-mail could not be sent.') . "<br />\n" . __('Possible reason: your host may have disabled the mail() function...') );

    return true;
}

$user_login = sanitize_text_field( $_GET['user_login'] );

if (retrieve_password($user_login)) {
    echo "SUCCESS";
} else {
    echo "ERROR";
}