Tutorial by Examples: copy

Copying file from/to containers

from container to host docker cp CONTAINER_NAME:PATH_IN_CONTAINER PATH_IN_HOST from host to container docker cp PATH_IN_HOST CONTAINER_NAME:PATH_IN_CONTAINER If I use jess/transmission from https://hub.docker.com/r/jess/transmission/builds/bsn7eqxrkzrhxazcuytbmzp/ , the files in the contai...

Docker • Managing containers

Copying Records while Changing Field Values

Suppose you have this type: data Person = Person { name :: String, age:: Int } deriving (Show, Eq) and two values: alex = Person { name = "Alex", age = 21 } jenny = Person { name = "Jenny", age = 36 } a new value of type Person can be created by copying from alex, specif...

Haskell Language • Record Syntax

Checking out a working copy at a specific revision

To get version 5394 use: svn co --revision r5394 https://svn.example.com/svn/MyRepo/MyProject/trunk Or the shorter version: svn co -r 5394 https://svn.example.com/svn/MyRepo/MyProject/trunk Or by using pegged revisions: svn co https://svn.example.com/svn/MyRepo/MyProject/trunk@5394 If al...

svn • Getting started with svn

Purpose of copy elision

There are places in the standard where an object is copied or moved in order to initialize an object. Copy elision (sometimes called return value optimization) is an optimization whereby, under certain specific circumstances, a compiler is permitted to avoid the copy or move even though the standard...

C++ • Copy Elision

Guaranteed copy elision

C++17 Normally, elision is an optimization. While virtually every compiler support copy elision in the simplest of cases, having elision still places a particular burden on users. Namely, the type who's copy/move is being elided must still have the copy/move operation that was elided. For example:...

C++ • Copy Elision

Copy initialization elision

If you use a prvalue expression to copy initialize a variable, and that variable has the same type as the prvalue expression, then the copying can be elided. std::string str = std::string("foo"); Copy initialization effectively transforms this into std::string str("foo"); (th...

C++ • Copy Elision

Copying too much

char buf[8]; /* tiny buffer, easy to overflow */ printf("What is your name?\n"); scanf("%s", buf); /* WRONG */ scanf("%7s", buf); /* RIGHT */ If the user enters a string longer than 7 characters (- 1 for the null terminator), memory behind the buffer buf will be...

C Language • Common pitfalls

Forgetting to copy the return value of realloc into a temporary

If realloc fails, it returns NULL. If you assign the value of the original buffer to realloc's return value, and if it returns NULL, then the original buffer (the old pointer) is lost, resulting in a memory leak. The solution is to copy into a temporary pointer, and if that temporary is not NULL, th...

C Language • Common pitfalls

Creating an immutable version of a type using defensive copying.

Some basic types and classes in Java are fundamentally mutable. For example, all array types are mutable, and so are classes like java.util.Data. This can be awkward in situations where an immutable type is mandated. One way to deal with this is to create an immutable wrapper for the mutable type...

Java Language • Immutable Objects

Cloning using a copy constructor

An easy way to clone an object is by implementing a copy constructor. public class Sheep { private String name; private int weight; public Sheep(String name, int weight) { this.name = name; this.weight = weight; } // copy constructor // copies...

Java Language • Object Cloning

Copy a Map

Like slices, maps hold references to an underlying data structure. So by assigning its value to another variable, only the reference will be passed. To copy the map, it is necessary to create another map and copy each value: // Create the original map originalMap := make(map[string]int) originalM...

Go • Maps

Copy to clipboard from textarea using execCommand("copy")

Example: <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title></title> </head> <body> <textarea id="content"></textarea> <input type="button" id="copy...

JavaScript • execCommand and contenteditable

Copying files by piping streams

This program copies a file using readable and a writable stream with the pipe() function provided by the stream class // require the file system module var fs = require('fs'); /* Create readable stream to file in current directory named 'node.txt' Use utf8 encoding Read the data...

Node.js • Filesystem I/O

Enable/Disable blank line copy

ctrl + alt + shift + / (cmd + alt + shift + / on MacOS) should show you the following dialog: Clicking on Registry you will get The key you want to enable/disable is editor.skip.copy.and.cut.for.empty.selection Tested on Linux Ubuntu and MacOS.

Android • Android Studio

Copy part of an Array

The slice() method returns a copy of a portion of an array. It takes two parameters, arr.slice([begin[, end]]) : begin Zero-based index which is the beginning of extraction. end Zero-based index which is the end of extraction, slicing up to this index but it's not included. If the end is a neg...

JavaScript • Arrays

Copy and swap

If you're writing a class that manages resources, you need to implement all the special member functions (see Rule of Three/Five/Zero). The most direct approach to writing the copy constructor and assignment operator would be: person(const person &other) : name(new char[std::strlen(other.n...

C++ • Special Member Functions

Copying files

To copy files from the build context in a Docker image, use the COPY instruction: COPY localfile.txt containerfile.txt If the filename contains spaces, use the alternate syntax: COPY ["local file", "container file"] The COPY command supports wildcards. It can be used for ...

Docker • Dockerfiles

Copying strings

Pointer assignments do not copy strings You can use the = operator to copy integers, but you cannot use the = operator to copy strings in C. Strings in C are represented as arrays of characters with a terminating null-character, so using the = operator will only save the address (pointer) of a str...

C Language • Strings

COPY Instruction

COPY has two forms: COPY <src>... <dest> COPY ["<src>",... "<dest>"] (this form is required for paths containing whitespace) The COPY instruction copies new files or directories from <src> and adds them to the filesystem of the container at the ...

Docker • Dockerfiles

Create a Copy of an Object with Certain Changes

Case classes provide a copy method that creates a new object that shares the same fields as the old one, with certain changes. We can use this feature to create a new object from a previous one that has some of the same characteristics. This simple case class to demonstrates this feature: case cla...

Scala Language • Case Classes