Currently (v380.64_2) there is no out-of-the-box mechanism to setup persistent crontabs which survives a system reboot. But there is a simple workaround availabe.

Your Crontab File#

First of all, create a standard crontab file and store it in your persistent JFFS partition. In this example /jffs/configs/cron

# Syntax
# MM HH DayOfMonth Month DayOfWeek <action>

# Run Backup Script at 4am
0 4 * * * /jffs/scripts/backup.sh

Setup Crontabs on startup#

To load the crontab list on boot, add the following line to your init-start script in /jffs/scripts/init-start

cp /jffs/configs/cron /var/spool/cron/crontabs/admin

That’s it!

Contact Form 7: Add Custom Data Providers to Select Elements/Tags

wordpress, wpcf7, select, values, database, lists, callback, programmatically

Every WordPress Power User knows the awesome Contact Form 7 plugin. It is (one of) the best plugins to create custom forms without any PHP knowledge – especially useful for endusers/customers.

But sometimes you need to create select list values programmatically. Unfortunately the Contact Form 7 Docs are very poor in matter of advanced use cases including the build-in filter hooks.

WPCF7 Form Editor#

Just add a unique name to the data attribute – in this example my.data.provider. This allows you to match the element within the filter hook!

<p>
<label> My List
    [select mylist include_blank data:my.data.provider]
</label>
</p>

Filter Hook#

Roll the drums…the magical filter hook wpcf7_form_tag_data_option allows you to alter the options list and add options/values to the select list within a simple callback

add_filter('wpcf7_form_tag_data_option', function($n, $options, $args){
    // special data provider tag found ?
    if (in_array('my.data.provider', $options)){
        return get_my_value_list();
    }

    // default - do not apply any changes within the options
    return null;
}, 10, 3);

Well, thats it!

HowTo: Wakeup your Synology NAS from Standby/Power Save Mode

timeout, linux, ubuntu, backup, scp, sftp, System Hibernation, backup

Scheduled Backups from Remote Locations#

As poweruser, you may have different servers out there which send their backups to a centralized backup location – in this example, a Synology NAS. The file transfers can be done by ftp, sftp, scp, nfs or another supported protocol.

In case you want to safe energy costs, it possible to enable the power safe mode which turns the system (as well as the HDDs) in standby mode. It can be waked-up by accessing the web-interface or some other file services, but this will take around 30-60s! In most cases, this behaviour will cause a timeout or connection refused error in your backup scripts. To prevent this, you can wake up your NAS before running the backup tasks. The following script tries to access the Web-Interface (DSM) on port 80 for a several times and returns 0 as exit code in case a valid response is returned by the remote server.

Wake-Up Script#

#!/bin/bash

# Synology NAS Wake-up
# ------------------------------------

# hostname/ip set ?
if [ -z "$1" ]; then
    echo "Usage: synology_wakeup.sh <hostname>"
    exit 1
fi

# get the server response. 5 connection tries with 10s delay -> 200s wait
serverResponse=$(wget --quiet --max-redirect=0 --retry-connrefused --timeout=20 --wait=10 --tries 5 --server-response -O /dev/null $1 2>&1)

# http detection pattern (response will be empty on con_refused)
detectionPattern="HTTP/1.1 (200|30[0-8])"

# server online ?
if [[ $serverResponse =~ $detectionPattern ]] ; then
    exit 0
else
    exit 1
fi

Usage#

Just run the script by passing the ip addess/hostname to it. On error (non responding nas) the script will return the exit code 1.

#!/bin/bash

# your backup/pre backup script

# wakeup your NAS by its IP/Hostname
./synology_wakeup.sh 192.168.0.100

# successfull ?
if [ $? -ne 0 ]; then
   echo "ERROR - Synology NAS seems to be offline!"
   exit 1
fi

 

 

 

Render Markdown/GFM Documents online using the GitHub v3 API

simple code snipped to convert markdown to html, public github api

Sometimes, you need to render parts of your Markdown documents – e.g. README.md or CHANGES.md – as html to embed it into your application, documentation or project website. There are a several markdown or especially GFM (GitHub Flavored Markdown) libraries are out there, but they require an additional setup and have to be maintained.

The simple Way#

Thanks to GitHub, there is a public API available which allows you to render your documents by the GitHub webservices.

PHP Client#

/**
 * Render Markdown content using the GitHub v3 Markdown API
 * @see https://developer.github.com/v3/markdown/
 * @source https://andidittrich.de/2016/05/render-markdown-gfm-documents-online-using-the-github-v3-api
 * @license: MIT
 * @return string(html)
 */
function renderGFM($text, $repositoryContext = null){

    // create the payload
    // @see https://developer.github.com/v3/markdown/
    $postdata = json_encode(
        array(
            'text' => $text,
            'mode' => ($repositoryContext != null ? 'gfm' : 'markdown'),
            'context' => $repositoryContext
        )
    );

    // prepare the HTTP 1.1 POST Request
    $opts = array('http' =>
        array(
            'method'  => 'POST',
            'protocol_version' => '1.1',
            'user_agent' => $repositoryContext,
            'header'  => array(
                'Content-type: application/x-www-form-urlencoded;charset=UTF-8',
                'Connection: close',
                'Accept: application/vnd.github.v3+json'
            ),
            'content' => $postdata
        )
    );

    // send request
    return file_get_contents('https://api.github.com/markdown', false, stream_context_create($opts));
}

Usage#

The optional $repositoryContext argument allows your to define the context which should be used for rendering to e.g. enable issue linking

// fetch the document (example)
$document = file_get_contents('https://raw.githubusercontent.com/AndiDittrich/WordPress.Enlighter/master/CHANGES.md');

// render html using the GitHub GFM API
$html = renderGFM($document, 'AndiDittrich/WordPress.Enlighter');

// show it!
echo $html;

 

 

You may have noticed, that normal users (especially Author’s and Contributor’s) are not allowed to use all kind of HTML Tags and related Attributes.

Those elements got removed by the WordPress buil-in KSES Filter – and it’s a very useful feature in matter of security to prevent html-code-injection.

But sometimes it is required to enable some additional html tags and/or attributes. You can modify the list of allowed html tags and attributes by appling a custom filter:

The Filter#

Example how to allow EnlighterJS related attributes for pre and code tags

function ksesAllowHtmlCodeAttributes($data, $context){
    // only apply filter on post-context
    if ($context === 'post'){

        // list of all available enlighterjs attributes
        $allowedAttributes = array(
            'data-enlighter-language' => true,
            'data-enlighter-theme' => true,
            'data-enlighter-group' => true,
            'data-enlighter-title' => true,
            'data-enlighter-linenumbers' => true,
            'data-enlighter-highlight' => true,
            'data-enlighter-lineoffset' => true
        );

        // apply to pre and code tags
        $data['pre'] = array_merge($data['pre'], $allowedAttributes);
        $data['code'] = array_merge($data['code'], $allowedAttributes);
    }

    return $data;
}

// add the filter function (2 arguments and priority 100)
add_filter('wp_kses_allowed_html', 'ksesAllowHtmlCodeAttributes', 100, 2);

 

 

 

Sometimes it can be very useful to have magical constants like __FILENAME__ or __LINE__ available within your sourcecode – especially for debugging or in merged files. Unfortunately, such feature is missing in javascript but it is possible to implement it by yourself using a file-postprocessing filter in your gulp build script. Thanks to gulp-concat-util, it’s […]

Prevent Errors from breaking Gulp watch

gulp-plumber, custom error handler, gulp-prettyerror

As an intermediate javascript developer, you may using gulp these days – a great and straightforward streaming build system with a lot of advantages compared to grunt. For example, i’ve switched from a bunch of custom, ANT based scripts to gulp for the next EnlighterJS major version and it saves a lot of time! Especially […]

Tweaking Minidlna Media Server on AsusWRT Merlin

usb storage, disable album arts, performance

You’re running AsusWRT Merlin and have some trouble with minidlna, e.g. bad media indexing performance or broken media databases ?

This can be caused by using an USB Stick as media database storage! Internally, minidlna is using an SQLite database to store the media file index – and sometime this database may broke (slow, unsynced file operations, user terminated processes).

As a workaround, it’s possible to move the media database to the temporary filesystem (ramdisk). As a disadvantage, on every system shutdown (reboot/power cycle) the database will be destroyed. But it only takes a view minutes to recreate it, because the ramdisk storage is a lot faster than the attached USB drive!

Just create an additional user config file in your JFFS /jffs/configs/minidlna.conf.add (will be automatically appended to the system generated minidlna.conf file!)

# Move the database to the tmp directory (ramdisk, will be recreated on reboot !!)
db_dir=/tmp/.minidlna

# create a custom minidlna logfile
log_dir=/var/log

# disable album art indexing
album_art_names=NO_ALBUM_ARTS.x

 

Single File ReCaptcha 2 PHP Client

leading captcha system, curl, php, json-response

Today, a web-form without a proven captcha system generates a lot of spam entries and data-trash in your database. One of the best is ReCaptcha (even the latest v2).

Google provides an easy to use ReCaptcha PHP Client – but it’s a bit over engineered! You need a bunch of PHP files and a composer based environment to use it out of the box. This can cause some trouble in highly customized/optimized projects.

Therefore, here is a “one-file” solution which works without any configuration overhead:

Usage#

require('ReCaptcha.php');

// register your secret
ReCaptcha::setSecret('<your-secret>');

// some code ...

// check user form
if (ReCaptcha::isValid()){ ...

One-File Solution#

// Developer Guide: https://developers.google.com/recaptcha/docs/verify
class ReCaptcha{

    // ReCaptcha API Endpoint
    const SITE_VERIFY_URL = 'https://www.google.com/recaptcha/api/siteverify';

    // the last result
    private static $_result = null;

    // client secret
    private static $_secret = null;

    // validate
    public static function isValid(){
        // token available ?
        if (!isset($_POST['g-recaptcha-response'])){
            return false;
        }

        // extract token
        $token = trim($_POST['g-recaptcha-response']);

        // generate url
        $params = http_build_query(array(
            'secret' => self::$_secret,
            'response' => $token,
            'remoteIp' => $_SERVER['REMOTE_ADDR']
        ), '', '&');

        // create curl based post request
        $handle = curl_init(self::SITE_VERIFY_URL);
        $options = array(
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => $params,
            CURLOPT_HTTPHEADER => array(
                'Content-Type: application/x-www-form-urlencoded'
            ),
            CURLINFO_HEADER_OUT => false,
            CURLOPT_HEADER => false,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_SSL_VERIFYPEER => true
        );
        curl_setopt_array($handle, $options);
        $response = curl_exec($handle);
        curl_close($handle);

        // decode response
        self::$_result = json_decode($response, true);

        // check
        return (self::$_result['success'] === true);
    }

    // error occurred ?
    public static function isError(){
        return (self::$_result['success'] === false);
    }

    // get error message from last request
    public static function getErrorMessages(){
        return self::$_result['error-codes'];
    }

    // set client secret
    public static function setSecret($s){
        self::$_secret = $s;
    }
}

 

Node.js Simple Command Line Confirm Messages

user confirmation, terminal actions, yes, no

Sometime, special terminal commands can be dangerous for your users. To ensure that they are really want to run the command the proven “best practise” is to wait for an explicit user confirmation by typing yes/no into the terminal.

Install “prompt” using NPM#

First of all, you have to install prompt – a powerfull package for command line prompts & user interactions. The “–save” option will add this package to your package.json file.

npm install prompt --save

Confirm Dialog#

After installing the prompt package you can use the following code to show a confirm dialog to your users.

var _prompt = require('prompt');

// user confirmation required!
_prompt.start();

// disable prefix message & colors
_prompt.message = '';
_prompt.delimiter = '';
_prompt.colors = false;

// wait for user confirmation
_prompt.get({
    properties: {
        
        // setup the dialog
        confirm: {
            // allow yes, no, y, n, YES, NO, Y, N as answer
            pattern: /^(yes|no|y|n)$/gi,
            description: 'Do you really want to format the filesystem and delete all file ?',
            message: 'Type yes/no',
            required: true,
            default: 'no'
        }
    }
}, function (err, result){
    // transform to lower case
    var c = result.confirm.toLowerCase();

    // yes or y typed ? otherwise abort
    if (c!='y' && c!='yes'){
        console.log('ABORT');
        return;
    }
    
    // your code
    console.log('Action confirmed');
    
});