4. June 2019

Cron / Crontab Tips Collection

I will use this article to collect interesting tips and tricks about using the Linux cron. This is not so much about setting up a cron, but about little things I use or discovered!

What is a cron ?

The cron daemon is a long-running process that executes commands at specific dates and times. You can use this to schedule activities, either as one-time events or as recurring tasks.

What is the crontab?

For commands that need to be executed repeatedly (e.g., hourly, daily, or weekly), you can use the crontab command. The crontab command creates a crontab file containing commands and instructions for the cron daemon to execute.

Format is: MIN HOUR DOM MON DOW CMD
Minute field
Hour field
Day of month
Day of week
Command

crontab -l    		# Viewing the cronjobs as currently logged in user 
crontab -e    		# Edit the cronjob for currently logged in user
crontab -l -u $USER 	# View the cronjob for the specified user 
crontab -e -u $USER	$ Edit the cronjob for the specified user

crontab -l # Viewing the cronjobs as currently logged in user

crontab -e # Edit the cronjob for currently logged in user

crontab -l -u $USER # View the cronjob for the specified user

crontab -e -u $USER $ Edit the cronjob for the specified user

Run every 5 minutes

*/5 * * * *  /home/reggaenights/script.sh

1	/5 * * * /home/reggaenights/script.sh

Run yearly, monthly, weekly, daily or on reboot.
@yearly will run at 00:00 on Jan 1st for every year.
@monthly will run at 00:00 on 1st of every month.
@weekly will run at 00:00 on starting of every week.
@daily will run at 00:00 on every day.
@reboot will run after the server has been rebooted

@yearly  	/home/reggaenights/script.sh	
@monthly 	/home/reggaenights/script.sh
@weekly		/home/reggaenights/script.sh
@daily  	/home/reggaenights/script.sh

@yearly /home/reggaenights/script.sh

@monthly /home/reggaenights/script.sh

@weekly /home/reggaenights/script.sh

@daily /home/reggaenights/script.sh

TIPS

1. Send cron output via email

*/30 * * * * /bin/bash /cleanup | /usr/bin/mail -s "Notify me" your@email.org

1	/30 * * * /bin/bash /cleanup \| /usr/bin/mail -s "Notify me" your@email.org

2. Use a real cron for WordPress

A real cron does not rely on website activity and executes independently.

*/30 * * * * /usr/bin/wget -q -O - https://yourwordpress.org/wp-cron.php?doing_wp_cron

1	/30 * * * /usr/bin/wget -q -O - https://yourwordpress.org/wp-cron.php?doing_wp_cron

Do not forget to disable the virtual WordPress Cron in the wp-config.php!

define('DISABLE_WP_CRON', true);

1	define('DISABLE_WP_CRON', true);

3. Prevent Emails being sent, when cron executes > /dev/null 2>&1

*/30 * * * * /usr/bin/wget -q -O - https://yourcrone.org/wp-cron.php?doing_wp_cron >/dev/null 2>&amp;1

1	/30 * * * /usr/bin/wget -q -O - https://yourcrone.org/wp-cron.php?doing_wp_cron >/dev/null 2>&1

4. Set Standard Variables

# Email to send output to
MAILTO="a@b.com,b@b.com"

# Setup your path for reuse
PATH="/usr/bin:/sbin:/bin"

# Tells which directory the cron should execute the crontab commands from
HOME="/path/to/app/root"

#Set the default shell
SHELL="/bin/bash"

# Email to send output to

MAILTO="a@b.com,b@b.com"

# Setup your path for reuse

PATH="/usr/bin:/sbin:/bin"

# Tells which directory the cron should execute the crontab commands from

HOME="/path/to/app/root"

#Set the default shell

SHELL="/bin/bash"

5. Output Redirection

*/15 * * * * /home/reggaenights/script.sh >> /home/collect/cron/output/pipe.log 2>&amp;1

1	/15 * * * /home/reggaenights/script.sh >> /home/collect/cron/output/pipe.log 2>&1

TOOLS

Crontab UI (NodeJS) – Easy way to edit your crontab visually. @Github
Chronis ( >= PHP 7) – Chronis will help you define cron jobs using natural language / YAML and will generate the crontab files for you. @Github
PHP Cron Expression Parser – Standard (V7) compliant crontab expression parser/validator with support for time zones. @Github
PhpGt/Cron (PHP) – Define background jobs in standard crontab format and the Cron Runner will execute them when they are due. Jobs can be either normal scripts, or calls to static functions with automatic autoloading taken care of. @Github
Cronicle (NodeJS) – A simple, distributed task scheduler and runner with a web based UI. @GitHub / Website

30. May 2019

Have you heard of GatsbyJS?

Gatsby is a free and open source framework based on React that helps developers build blazing fast websites and apps.

What they have to say …

Go Beyond Static Websites. Get all the benefits of static websites with none of the limitations. Gatsby sites are fully functional React apps so you can create high-quality, dynamic web apps, from blogs to e-commerce sites to user dashboards.
Use a Modern Stack for Every Site. No matter where the data comes from, Gatsby sites are built using React and GraphQL. Build a uniform workflow for you and your team, regardless of whether the data is coming from the same backend.
Load Data From Anywhere. Gatsby pulls in data from any data source, whether it’s Markdown files, a headless CMS like Contentful or WordPress, or a REST or GraphQL API. Use source plugins to load your data, then develop using Gatsby’s uniform GraphQL interface.
Performance Is Baked In. Ace your performance audits by default. Gatsby automates code splitting, image optimization, inlining critical styles, lazy-loading, and prefetching resources, and more to ensure your site is fast — no manual tuning required.
Host at Scale for Pennies. Gatsby sites don’t require servers so you can host your entire site on a CDN for a fraction of the cost of a server-rendered site. Many Gatsby sites can be hosted entirely free on services like GitHub Pages and Netlify.

What I have to say …

While researching some popular static site generation tools, GatsbyJS comes up often. I have played with NuxtJS and Hugo in the past, but what I REALLY like about GatsbyJS is the plugin / modular system. You can build your website with plain-old React and CSS styles, but make your development more efficient by adding node_modules.

Also being able to import any data source with ease, using GraphQL, is amazing. And when it comes to content management, you can easily hook a headless WordPress or Drupal setup into the mix and consume their REST APIs :)

I am not switching my own website to GatsbyJS anytime soon, but its another tool in my toolbox for future project consideration !

There are many tutorials on Youtube about getting started, maybe something to consider for the next freetime testdrive ;) Enjoy …

GatsbyJS @ Github

20. May 2019

PsySH – PHP Debug Console

A runtime developer console, interactive debugger and REPL for PHP.

PsySH can be used as an interactive debugger, much like JavaScript’s debugger statement, saving you from endless var_dump() and die() iterations. Just drop this line in where you’d like to have a breakpoint: eval(\Psy\sh());
PsySH has tab completion for variable names, functions, classes, methods, properties, and even files! Just start typing, then hit [tab]. But you probably already guessed that.
Most PHP shells are terrible at namespaces. PsySH does just what you’d expect.
Have a question about a core PHP function? Try doc array_map. Want to read the documentation for an object property? Run doc $response->statusTexts.
The list command knows all about your code — and everyone else’s. Easily list and search all variables, constants, classes, interfaces, traits, functions, methods and properties.
Easily show the source code for any userland object, class, interface, trait, constant, method or property.
No worries, PsySH has your back. We caught it for you, and made it available via the wtf command.
Show, search, save and replay your shell history.
and much more :)

Integrations

CakePHP: cake console
CiviCRM: cv cli
CodeIgniter: craftsman console
Drupal: drush php, drupal shell
Emacs: psysh.el
eZ Publish: ezsh
Grav: bin/plugin psysh shell
Jupyter: Jupyter-PHP
Laravel/Lumen: artisan tinker
Magento: magerun console
MediaWiki: php maintenance/shell.php
Pantheon CLI: terminus cli console
Phalcon: phalcon console
SilverStripe: sliver
Symfony: sf1-psysh-bootstrap
Symfony2: PsyshBundle, symfony-repl
WordPress: wp-cli shell
Yii 2: yii shell
Zend Framework 1: zf1-psysh
Zend Framework 2: PsyshModule

Github
Website

18. May 2019

Screenshot Service with Node.js

Manet is a REST API server which allows capturing screenshots of websites using various parameters.

The Node.js server can use SlimerJS or PhantomJS as headless browser engines.

I have build similar with CasperJS, but this is far better for those that want a simple straight solution.

@GitHub

17. May 2019

CSS3 Animations with Special Effects.

A nice set of CSS3 Animations that can be easily used to spice up your design.

The animations can be triggered through Javascript, jQuery and the timings can be tweaked through pure CSS. The package also provides gulp, so that you can tweak every aspect easily.

Demo
Github

15. May 2019

A Helping Hand for Image & CSS Sprites

SPRITEOWL is a Photoshop extension that takes over the boring part of working with sprite images and CSS.
Retrieves x, y, width and height info of all sprite elements
Exports retina ready PNG files and required media queries of your Photoshop sprite file
Supports preprocessors LESS, SASS/SCSS & Stylus
Spriteowl
CSSOWL is a mixin library that works with Spriteowl.
LESS, SASS/SCSS & Stylus support
Open source
Cssowl

Two tools that can enhance your workflow immensely. Enjoy!

15. May 2019

ZombieLoad Attack

“After Meltdown, Spectre, and Foreshadow, we discovered more critical vulnerabilities in modern processors. The ZombieLoad attack allows stealing sensitive data and keys while the computer accesses them. While programs normally only see their own data, a malicious program can exploit the fill buffers to get hold of secrets currently processed by other running programs. These secrets can be user-level secrets, such as browser history, website content, user keys, and passwords, or system-level secrets, such as disk encryption keys.” – zombieloadattack.com

There seems to be a new security related story every day. Read about the latest CPU related issues at CPU.fail.

11. May 2019

portalZINE goes Multi-Language

Since I started in 2002, all iterations of portalZINE have been pure english content websites. You can read about the why on my services page.

I had potential customers in Germany complain about that a lot over the past few years. But your own website often suffers, while your customers get all the attention. That is how it is and how it should be!

Creating Multi – Language websites has been part of my services & portfolio for years, with an extreme application setup handling 13 languages in 2014 for the soccer world cup.

Multi-Language setups have come a long way and it was time to showcase that on my own setup as well. Not only to calm those potential customers, but to testdrive new functionality and possibilities on my own setup. portalZINE has always been my testlab for stability and new feature sets.

Most of my static pages are available in English and German now, the blog itself will remain pure English.

Need help setting up a multi language website, get in touch!

Cheers
Alex

10. May 2019

Composercat – a GUI for composer

Composercat is a comprehensive GUI for the Composer package manager, designed both for professionals and people taking their first steps with Composer.

A nice entry point for everyone that is afraid of the console. The GUI application is currently in beta and available for Windows, MacOS and Linux.

“Composer is a tool for dependency management in PHP. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you.”

Composercat
Composer

19. April 2019

Happy Easter 2019

I am taking a small easter break to join up with family and friends. We will have perfect weather up here in the north for the coming days.

I wish you all Happy Easter and many lovely days away from routine business life.

Enjoy
Alex