Filesystem and I/O

Terminal I/O, path processing, and filesystem access are provided by std.io, std.path, and std.fs, respectively.

Standard Input and Output

import std.io;

print("Name: ");
let name = readLine();
println("Hello, {0}", name);

print does not append a newline; println does. stdio provides lower-level byte I/O, standard-error output, and line-based reading:

stdio.writeErrorLine("warning");

Paths

std.path processes strings without accessing the filesystem:

import std.path;

let path = join("data", "users", "alice.json");
let parent = dirname(path);
let name = basename(path);
let extension = extname(path);
let normalized = normalize("data/./users/../config");

The path separator is always /. resolve(base, target) uses the base supplied by the caller and does not read the current working directory.

File Convenience Functions

import std.fs;

writeText("message.txt", "Hello, world!");
let content = readText("message.txt");

if exists("message.txt") && isFile("message.txt") {
  rename("message.txt", "greeting.txt");
}

Other functions include readBytes, writeBytes, stat, isDir, and remove.

Explicit File Lifetime

let file = File.create("data.bin", FileMode.ReadWriteCreate);
defer {
  file.close();
}

file.writeText("Feng");

File provides byte and text I/O, status queries, and an explicit close(). A closed file cannot be read or written.

Directories

mkdir("output");
let entries = readDir("output");

let directory = Dir.create(".");
defer {
  directory.close();
}

for let entry in directory {
  println(entry.name);
}

Directory iteration yields EntryInfo values whose kind is represented by EntryKind. Filesystem errors are reported as Feng exceptions.