Understanding Heredocs in Dockerfiles

As of a couple weeks ago, Docker’s BuildKit tool for building Dockerfiles now supports heredoc syntax! With these new improvements, we can do all sorts of things that were difficult before, like multiline RUNs without needing all those pesky backslashes at the end of each line, or the creation of small inline configuration files.

In this post, I’ll cover the basics of what these heredocs are, and more importantly what you can use them for, and how to get started with them!

#docker 

What is GEEK

Buddha Community

Understanding Heredocs in Dockerfiles

As of a couple weeks ago, Docker’s BuildKit tool for building Dockerfiles now supports heredoc syntax! With these new improvements, we can do all sorts of things that were difficult before, like multiline RUNs without needing all those pesky backslashes at the end of each line, or the creation of small inline configuration files.

In this post, I’ll cover the basics of what these heredocs are, and more importantly what you can use them for, and how to get started with them!

#docker 

How to Create Dockerfile Nedir | Dockerfile Nedir | Docker Tutorial #9

Bu videoda Docker Image’lar oluşturabilmek için gerekli olan Dockerfile’dan ve nasıl kullanıldığından bahsettim. Kendi kodları ve yazım formatı olan bu dosya ile kendi Image’larınızı oluşturabilir ve bunları Container’lar içerisinde çalıştırabilirsiniz.

In this video, I have mentioned what is Dockerfile and how to use Dockerfile. It has its own commands and syntax. By using these commands, you may build your own Image and execute it in a Docker Container.

Dockerfile Oluşturma
Dockerfile Komutları
How to create Dockerfile

#docker #dockerimage #dockerfile #dockercontainer

#docker #dockercontainer #dockerimage #dockerfile

Guide to Understanding Generics in Java

Introduction

Java is a type-safe programming language. Type safety ensures a layer of validity and robustness in a programming language. It is a key part of Java’s security to ensure that operations done on an object are only performed if the type of the object supports it.

Type safety dramatically reduces the number of programming errors that might occur during runtime, involving all kinds of errors linked to type mismatches. Instead, these types of errors are caught during compile-time which is much better than catching errors during runtime, allowing developers to have less unexpected and unplanned trips to the good old debugger.

Type safety is also interchangeably called strong typing.

Java Generics is a solution designed to reinforce the type safety that Java was designed to have. Generics allow types to be parameterized onto methods and classes and introduces a new layer of abstraction for formal parameters. This will be explained in detail later on.

There are many advantages of using generics in Java. Implementing generics into your code can greatly improve its overall quality by preventing unprecedented runtime errors involving data types and typecasting.

This guide will demonstrate the declaration, implementation, use-cases, and benefits of generics in Java.

#java #guide to understanding generics in java #generics #generics in java #guide to understanding generics in java

Bash Heredoc and Using Heredoc with SSH

When writing shell scripts you may be in a situation where you need to pass a multiline block of text or code to an interactive command, such as [tee](https://linuxize.com/post/linux-tee-command/), cat, or [sftp](https://linuxize.com/post/how-to-use-linux-sftp-command-to-transfer-files/).

In Bash and other shells like Zsh, a Here document (Heredoc) is a type of redirection that allows you to pass multiple lines of input to a command.

The syntax of writing HereDoc takes the following form:

[COMMAND] <<[-] 'DELIMITER'
  HERE-DOCUMENT
DELIMITER

Copy

• The first line starts with an optional command followed by the special redirection operator << and the delimiting identifier.
• You can use any string as a delimiting identifier, the most commonly used are EOF or END.
• If the delimiting identifier is unquoted, the shell will substitute all variables, commands and special characters before passing the here-document lines to the command.
• Appending a minus sign to the redirection operator <<-, will cause all leading tab characters to be ignored. This allows you to use indentation when writing here-documents in shell scripts. Leading whitespace characters are not allowed, only tab.
• The here-document block can contain strings, variables, commands and any other type of input.
• The last line ends with the delimiting identifier. White space in front of the delimiter is not allowed.

Basic Heredoc Examples

In this section, we will look at some basic examples of how to use heredoc.

Heredoc is most often used in combination with the cat command.

#bash #bash heredoc #ssh

Dockerfile and Its Components

Dockerfile is basically a text file. It contains some set of instructions. Automation of docker image creation.

Docker Components =>

FROM: for a base image the command must be on top of the docker

RUN: To execute Command, it will create a layer in the image.

MAINTAINER: Author/owner/description

COPY: Copy files from the local system (docker VM) we need to provide a source, destination(We cant download file from the internet and any remote directory)

ADD: Similar to copy but, it provides a feature to download files from the internet, also we extract files at the docker image side.

EXPOSE: To Expose ports such as port 8080 for tomcat, port 80 for Nginx, etc.

WORKDIR: To set a working directory for a container.

CMD: Execute commands but during container creation

ENTRYPOINT: Similar to CMD, but has higher priority over CMD, first commands will be executed by ENTRYPOINT only.

#devops #docker #dockerfiles #containerization