File

C

#include <stdio.h>

FILE *file = fopen("example.txt", "r");
if (file != NULL)
{
	char line[256];
	while (fgets(line, sizeof line, file) != NULL)
	{
		printf("%s", line);
	}
	fclose(file);
}

C++

#include <fstream>
#include <string>

std::ifstream file {"example.txt"};
std::string line;

while (std::getline(file, line))
{
	std::cout << line << '\n';
}

C#

string text = File.ReadAllText("example.txt");
File.WriteAllText("output.txt", text);

foreach (string line in File.ReadLines("example.txt"))
{
	Console.WriteLine(line);
}

Java

// Since Java 11 for Files.readString/writeString
String text = Files.readString(Path.of("example.txt"));
Files.writeString(Path.of("output.txt"), text);

List<String> lines = Files.readAllLines(Path.of("example.txt"));

Rust

use std::fs;

let text = fs::read_to_string("example.txt")?;
fs::write("output.txt", text)?;

Go

content, err := os.ReadFile("example.txt")
if err != nil {
	return err
}

err = os.WriteFile("output.txt", content, 0644)

Javascript

// Node.js
import { readFile, writeFile } from 'node:fs/promises';

const text = await readFile('example.txt', 'utf8');
await writeFile('output.txt', text);

Typescript

// Node.js
import { readFile, writeFile } from 'node:fs/promises';

const text: string = await readFile('example.txt', 'utf8');
await writeFile('output.txt', text);

Python

from pathlib import Path

text = Path("example.txt").read_text(encoding="utf-8")
Path("output.txt").write_text(text, encoding="utf-8")

with open("example.txt", encoding="utf-8") as file:
	for line in file:
		print(line, end="")