Tutorial by Examples: ha

Installing ZSH as default shell on macOS

The simplest way is to use brew: brew install zsh After installation, you may want to set it as your default shell by doing: sudo echo '/usr/local/bin/zsh' >> /etc/shells chsh -s /usr/local/bin/zsh If you have git, and required command line tools installed you can compile and install ...

command-line • Getting started with command-line

What is puppet and why should I care?

Puppet is a configuration management solution. Users describe the desired state of a server or software and configuration management achieves this state. This brings following advantages: Configurations can be reproduced exactly the same every time, as many times as necessary Configurations for ...

puppet • Getting started with puppet

Using ShellSharp

When you need multi level menus, with multiple parameters SharpShell comes to rescue. https://github.com/dwmkerr/sharpshell has umpteen number of examples and it works perfect even for single level to multi level custom context menus. Key thing is to create class with attributes [ComVisible(true)]...

Windows • Programming Custom Desktop File/Folder context menu extensions

Creating a chart

The chart consists out of HTML container and the JavaScript code that instantiates a chart in it. HTML We use a <div> element as chart container. <div id="chartdiv" style="height: 300px;"></div> JavaScript To instantiate the chart we use AmCharts.makeChar...

amcharts • Getting started with amcharts

Authentication handler

public class AuthenticationHandler : DelegatingHandler { /// <summary> /// Holds request's header name which will contains token. /// </summary> private const string securityToken = "__RequestAuthToken"; /// <summary> ...

C# Language • C# Authentication handler

Entering special characters in strings and regular expressions

Most printable characters can be included in string or regular expression literals just as they are, e.g. var str = "ポケモン"; // a valid string var regExp = /[Α-Ωα-ω]/; // matches any Greek letter without diacritics In order to add arbitrary characters to a string or regular expression,...

JavaScript • Escape Sequences

What is a Consumer Group

As of Kafka 0.9, the new high level KafkaConsumer client is availalbe. It exploits a new built-in Kafka protocol that allows to combine multiple consumers in a so-called Consumer Group. A Consumer Group can be describes as a single logical consumer that subscribes to a set of topics. The partions ov...

apache-kafka • Consumer Groups and Offset Management

With Apache Maven

The JasperReports-plugin by Alex Nederlof is a good alternative of abandoned org.codehaus.mojo:jasperreports-maven-plugin plugin. The adding of plugin is a typical, simple procedure: <build> <plugins> <plugin> <groupId>com.alexnederlof</groupId...

jasper-reports • Compile JasperReports .jrxml to .jasper

What, when and Why?

When the shell performs parameter expansion, command substitution, variable or arithmetic expansion, it scans for word boundaries in the result. If any word boundary is found, then the result is split into multiple words at that position. The word boundary is defined by a shell variable IFS (Interna...

Bash • Word splitting

Looping through a file line by line

while IFS= read -r line; do echo "$line" done <file If file may not include a newline at the end, then: while IFS= read -r line || [ -n "$line" ]; do echo "$line" done <file

Bash • Read a file (data stream, variable) line-by-line (and/or field-by-field)?

Looping through a string line by line

var='line 1 line 2 line3' while IFS= read -r line; do echo "-$line-" done <<< "$var" or readarray -t arr <<< "$var" for i in "${arr[@]}";do echo "-$i-" done

Bash • Read a file (data stream, variable) line-by-line (and/or field-by-field)?

Get captured groups from a regex match against a string

a='I am a simple string with digits 1234' pat='(.*) ([0-9]+)' [[ "$a" =~ $pat ]] echo "${BASH_REMATCH[0]}" echo "${BASH_REMATCH[1]}" echo "${BASH_REMATCH[2]}" Output: I am a simple string with digits 1234 I am a simple string with digits 1234

Bash • Pattern matching and regular expressions

Splitting by separator changes

We can just do simple replacement of separators from space to new line, as following example. echo $sentence | tr " " "\n" It'll split the value of the variable sentence and show it line by line respectively.

Bash • Word splitting

Pie Chart with Demo

<!doctype html> <html> <head> <style> body{ background-color:white; } #canvas{border:1px solid red; } </style> <script> window.onload=(function(){ var canvas = document.getElementById("canvas"); var ctx = canvas.getContext(&...

html5-canvas • Charts & Diagrams

A function that accepts named parameters

foo() { while [[ "$#" -gt 0 ]] do case $1 in -f|--follow) local FOLLOW="following" ;; -t|--tail) local TAIL="tail=$2" ;; esac shift done echo "FOLLOW: $FOLLOW" echo "TAIL: $...

Bash • Functions

Rotate an Image or Path around it's centerpoint

Steps#1-5 below allow any image or path-shape to be both moved anywhere on the canvas and rotated to any angle without changing any of the image/path-shape's original point coordinates. Move the canvas [0,0] origin to the shape's center point context.translate( shapeCenterX, shapeCenterY ); ...

html5-canvas • Transformations

basic channel operations: creating, putting, taking, closing, and buffers.

core.async is about making processes that take values from and put values into channels. (require [clojure.core.async :as a]) Creating channels with chan You create a channel using the chan function: (def chan-0 (a/chan)) ;; unbuffered channel: acts as a rendez-vous point. (def chan-1 (a/chan...

clojure • core.async

.has

Determine if an object has (or contains) a key. If the key to search for is expressed as a path (with dot notation) it will traverse nested object structures to determine if the key exists. var obj = { a: 2, b: 3, c: { dd:40, ee:{ fff:500 } } }; var res1 = _.ha...

lodash • Working with objects

Have an INDEX

The most important thing for speeding up a query on any non-tiny table is to have a suitable index. WHERE a = 12 --> INDEX(a) WHERE a > 12 --> INDEX(a) WHERE a = 12 AND b > 78 --> INDEX(a,b) is more useful than INDEX(b,a) WHERE a > 12 AND b > 78 --> INDEX(a) or INDE...

MySQL • Performance Tuning

Firebase Realtime DataBase event handler

First Initialize FirebaseDatabase: FirebaseDatabase database = FirebaseDatabase.getInstance(); Write to your database: // Write a message to the database FirebaseDatabase database = FirebaseDatabase.getInstance(); DatabaseReference myRef = database.getReference("message"); myRef....

Android • Firebase Realtime DataBase