Files & IO

These modules cover the first practical “real program” tasks:

• read and write files
• print text
• read a line from the terminal

std.fs

Use std.fs for local file and directory work.

import std.fs as fs;

Current API:

• fs.exists(str) -> bool
• fs.cwd() -> result str
• fs.create_dir(str) -> result bool
• fs.remove_dir(str) -> result bool
• fs.read_text(str) -> result str
• fs.file_size(str) -> result int
• fs.copy(str, str) -> result bool
• fs.write_text(str, str) -> result bool
• fs.append_text(str, str) -> result bool
• fs.rename(str, str) -> result bool
• fs.move(str, str) -> result bool
• fs.remove(str) -> result bool

Small example

import std.strings as strings;
import std.fs as fs;

fn:int main() {
    let text:str = strings.copy("demo");
    let write_ok:result bool = fs.write_text("build/demo.txt", text);
    if write_ok.ok == false {
        free text;
        return 1;
    }

    let size:result int = fs.file_size("build/demo.txt");
    if size.ok == false {
        free text;
        return 2;
    }

    free text;
    return 0;
}

What to notice:

• file operations can fail, so many return result ...
• strings.copy(...) created owned text, so it is freed

std.io

Use std.io for terminal-style input/output.

import std.io as io;

Current API:

• io.write(str) -> void
• io.write_line(str) -> void
• io.read_line() -> str

Small example

import std.io as io;
import std.strings as strings;

fn:int main() {
    let name:str = io.read_line();
    let message:str = strings.concat("hello ", name);
    io.write_line(message);
    free name;
    free message;
    return 0;
}

ownership

io.read_line() returns an owned string. Free it after use.

Beginner recommendation

If you are new, start with:

• io.write_line(...)
• io.read_line()
• fs.write_text(...)
• fs.read_text(...)

That gives you enough to build small text tools very quickly.