Tutorial by Examples: r

Look at the contents of /etc/redhat-release cat /etc/redhat-release Here is the output from a Fedora 24 machine: Fedora release 24 (Twenty Four) As mentioned in the debian-based response, you can also use the lsb_release -a command, which outputs this from a Fedora 24 machine: LSB Version: ...

ReactJS is an open-source, component based front end library responsible only for the view layer of the application. It is maintained by Facebook. ReactJS uses virtual DOM based mechanism to fill in data (views) in HTML DOM. The virtual DOM works fast owning to the fact that it only changes individ...

GroupBy is an easy way to sort a IEnumerable<T> collection of items into distinct groups. Simple Example In this first example, we end up with two groups, odd and even items. List<int> iList = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; var grouped = iList.GroupBy(x => x ...

Post::find()->all(); // SELECT * FROM post or the shorthand (Returns an active record model instance by a primary key or an array of column values.) Post::findAll(condition); returns an array of ActiveRecord instances. Find All with where Condition $model = User::find() ->w...

OPERATORS $postsGreaterThan = Post::find()->where(['>', 'created_at', '2016-01-25'])->all(); // SELECT * FROM post WHERE created_at > '2016-01-25' $postsLessThan = Post::find()->where(['<', 'created_at', '2016-01-25'])->all(); // SELECT * FROM post WHERE created_at < '2...

<?php namespace models; use yii\db\ActiveRecord; use yii\behaviors\TimestampBehavior; class Post extends ActiveRecord { public static function tableName() { return 'post'; } public function rules() { ...

Generators can be used to implement coroutines: # create and advance generator to the first yield def coroutine(func): def start(*args,**kwargs): cr = func(*args,**kwargs) next(cr) return cr return start # example coroutine @coroutine def adder(sum = 0): ...

To get your most recent stash after running git stash, use git stash apply To see a list of your stashes, use git stash list You will get a list that looks something like this stash@{0}: WIP on master: 67a4e01 Merge tests into develop stash@{1}: WIP on master: 70f0d95 Add user role to lo...

You have to keep the operator precedence in mind when using await keyword. Imagine that we have an asynchronous function which calls another asynchronous function, getUnicorn() which returns a Promise that resolves to an instance of class Unicorn. Now we want to get the size of the unicorn using th...

async functions do not replace the Promise type; they add language keywords that make promises easier to call. They are interchangeable: async function doAsyncThing() { ... } function doPromiseThing(input) { return new Promise((r, x) => ...); } // Call with promise syntax doAsyncThing() ...

When accessing arrays with pointers, there are no bounds check and therefore no IndexOutOfRangeException will be thrown. This makes the code faster. Assigning values to an array with a pointer: class Program { static void Main(string[] args) { unsafe { int...

The Oracle SQL and PL/SQL || operator allows you to concatenate 2 or more strings together. Example: Assuming the following customers table: id firstname lastname --- ----------- ---------- 1 Thomas Woody Query: SELECT firstname || ' ' || lastname || ' is in my database.' a...

CSS3 introduces a few new units, including the rem unit, which stands for "root em". Let's look at how rem works. First, let's look at the differences between em and rem. em: Relative to the font size of the parent. This causes the compounding issue rem: Relative to the font size of t...

Interaction with the history # List all previous commands history # Clear the history, useful if you entered a password by accident history -c Event designators # Expands to line n of bash history !n # Expands to last command !! # Expands to last command starting with "text&qu...

Prerequisites Installation

Prerequisites Installation

The second value in the curly braces dictates the length of the replacement string. By adjusting the second value to be positive or negative, the alignment of the string can be changed. string.Format("LEFT: string: ->{0,-5}<- int: ->{1,-5}<-", "abc", 123); string....

// Integral types as hex string.Format("Hexadecimal: byte2: {0:x2}; byte4: {0:X4}; char: {1:x2}", 123, (int)'A'); // Integers with thousand separators string.Format("Integer, thousand sep.: {0:#,#}; fixed length: >{0,10:#,#}<", 1234567); // Integer with leading zero...

Use existing .NET classes instantly with PowerShell by using [class]::Method(args): PS C:\> [guid]::NewGuid() Guid ---- 8874a185-64be-43ed-a64c-d2fe4b6e31bc Similarly, in PowerShell 5+ you may use the New-Guid cmdlet: PS C:\> New-Guid Guid ---- 8874a185-64be-43ed-a64c-d2fe4b6e31...

import std.stdio; // Let's get going! void main() { writeln("Hello World!"); } To compile and run, save this text as a file called main.d. From the command line run dmd main.d to compile the program. Finally, run ./main to execute the program in a bash shell or you can click ...