Tutorial by Examples: ch

@echo off prevents the prompt and contents of the batch file from being displayed, so that only the output is visible. The @ makes the output of the echo off command hidden as well.

Ways to create a file with the echo command: ECHO. > example.bat (creates an empty file called "example.bat") ECHO message > example.bat (creates example.bat containing "message") ECHO message >> example.bat (adds "message" to a new line in example.bat)...

DispatchGroup allows for aggregate synchronization of work. You can use them to submit multiple different work items and track when they all complete, even though they might run on different queues. This behavior can be helpful when progress can’t be made until all of the specified tasks are c...

DispatchSemaphore provides an efficient implementation of a traditional counting semaphore, which can be used to control access to a resource across multiple execution contexts. A scenario for when to use a semaphore could be if you are doing some file reading/writing, if multiple tasks are t...

Swift 3 Serial Queue func serialQueues () { let serialQueue = DispatchQueue(label: "com.example.serial") //default queue type is a serial queue let start = Date () for i in 0...3 { //launch a bunch of tasks serialQueue.a...

This example echoes the special character ! into a file. This would only work when DelayedExpansion is disabled. When delayed expansion in enabled, you will need to use three carets and an exclamation mark like this: @echo off setlocal enabledelayedexpansion echo ^^^!>file echo ^>>&...

You can enhance your kernel by adding new I/O schedulers if needed. Globally, governors and schedulers are the same; they both provide a way how the system should work. However, for the schedulers it is all about the input/output datastream except for the CPU settings. I/O schedulers decide how an u...

g + geom_bar(mapping = aes(x = cut, fill = clarity), position = "dodge") + theme(axis.text = element_text(colour = "red", size = 12))

This is the typical approach for novice developers building SQL action queries. They are vulnerable to the Bobby Tables type SQL Injection attacks. Dim strSQL As String strSQL = "INSERT INTO Employees chrFirstName, chrLastName, chrPhone " _ & "VALUES ('" & M...

This approach will prevent a user from embedding a second SQL statement in their input for execution. Dim strSQL As String Dim db As DAO.Database Dim qdf As DAO.QueryDef strSQL = "PARAMETERS [FirstName] Text(255), [LastName] Text(255), [Phone] Text(255); " _ & "INS...

Let's apply the State Machine pattern for parsing lines with the specific pattern using S4 Class feature from R. PROBLEM ENUNCIATION We need to parse a file where each line provides information about a person, using a delimiter (";"), but some information provided is optional, and instea...

UILabel, UITextField, & UITextView classes have a new property starting from iOS 10 for automatically resizing their font when a user changes their preferred reading size named adjustsFontForContentSizeCategory. Swift @IBOutlet var label:UILabel! if #available(iOS 10.0, *) { label.adju...

ASP.Net exposes Cache API to store data in the cache for retrieval later. Getting Started Store string Cache["key"]="value"; Retrieve string var value=""; if (Cache["key"] != null) value = Cache["key"].ToString(); You can also use t...

You can use Try..Catch to rollback database operation by placing the rollback statement at the Catch Segment. Try 'Do the database operation... xCmd.CommandText = "INSERT into ...." xCmd.ExecuteNonQuery() objTrans.Commit() ...

Although Catch ex As Exception claims that it can handle all exceptions - there are one exception (no pun intended). Imports System Static Sub StackOverflow() ' Again no pun intended StackOverflow() End Sub Static Sub Main() Try StackOverflow() Catch ex As Exception ...

Create a service- import {EventEmitter} from 'angular2/core'; export class NavService { navchange: EventEmitter<number> = new EventEmitter(); constructor() {} emitNavChangeEvent(number) { this.navchange.emit(number); } getNavChangeEmitter() { return...

Sometimes, you need to output to more than one index in ElasticSearch, or have a custom mapping you want to apply to new indices as they roll in. There are two ways to apply a custom mapping. One way, is to upload an ElasticSearch template. See the ElasticSearch documentation for that. The other ...

You should go to Xcode -> Open Developer Tool: Using "Simulator", you could run iOS and tvOS, but "Simulator (Watch)" will only run watchOS.

Go to Hardware -> Touch Pressure: To simulate a normal press, use Shift-Command-1 and a deep one, Shift-Command-2. If your MacBook has a Force Touch trackpad, you could use your trackpad force to simulate 3D / Force Touch.

Go to Hardware -> Device: