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103 lines
4.0 KiB
Zig
103 lines
4.0 KiB
Zig
//
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// Until now, we've only been printing our output in the console,
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// which is good enough for fighting aliens and hermit bookkeeping.
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//
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// However, many other tasks require some interaction with the file system,
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// which is the underlying structure for organizing files on your computer.
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//
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// The file system provides a hierarchical structure for storing files
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// by organizing them into directories, which hold files and other directories,
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// thus creating a tree structure that can be navigated.
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//
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// Fortunately, the Zig Standard Library provides a simple API for interacting
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// with the file system, see the detail documentation here:
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//
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// https://ziglang.org/documentation/master/std/#std.Io
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//
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// In this exercise, we'll try to:
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// - create a new directory,
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// - open a file in the directory,
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// - write to the file.
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//
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// Note: For simplicity, we write byte-by-byte without buffering.
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// In real applications, you'd typically use a buffer for better
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// performance. We'll learn about buffered I/O in a later exercise.
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//
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const std = @import("std");
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pub fn main(init: std.process.Init) !void {
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// default I/O implementation
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const io = init.io;
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// first we get the current working directory
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const cwd: std.Io.Dir = std.Io.Dir.cwd();
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// then we'll try to make a new directory /output/
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// to store our output files.
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cwd.createDir(io, "output", .default_dir) catch |e| switch (e) {
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// there is a chance you might want to run this
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// program more than once and the path might already
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// have been created, so we'll have to handle this error
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// by doing nothing
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//
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// we want to catch error.PathAlreadyExists and do nothing
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??? => {},
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// if there's any other unexpected error we just propagate it through
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else => return e,
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};
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// then we'll try to open our freshly created directory
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// wait a minute...
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// opening a directory might fail!
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// what should we do here?
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var output_dir: std.Io.Dir = try cwd.openDir(io, "output", .{});
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defer output_dir.close(io);
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// we try to open the file `zigling.txt`,
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// and propagate any error up
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const file: std.Io.File = try output_dir.createFile(io, "zigling.txt", .{});
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// it is a good habit to close a file after you are done with it
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// so that other programs can read it and prevent data corruption
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// but here we are not yet done writing to the file
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// if only there were a keyword in Zig that
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// allowed you to "defer" code execution to the end of the scope...
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file.close(io);
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// you are not allowed to move these lines above the file closing line!
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var file_writer = file.writer(io, &.{});
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const writer = &file_writer.interface;
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const byte_written = try writer.write("It's zigling time!");
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std.debug.print("Successfully wrote {d} bytes.\n", .{byte_written});
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}
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// to check if you actually write to the file, you can either,
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// 1. open the file in your text editor, or
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// 2. print the content of the file in the console with one of these commands
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// Linux/macOS: >> cat ./output/zigling.txt
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// Windows (CMD): >> type .\output\zigling.txt
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//
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//
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// More on Creating files
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//
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// notice in:
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// ... try output_dir.createFile(io, "zigling.txt", .{});
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// ^^^
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// we passed this anonymous struct to the function call
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//
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// this is the struct `CreateFlag` with default fields
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// {
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// read: bool = false,
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// truncate: bool = true,
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// exclusive: bool = false,
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// lock: Lock = .none,
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// lock_nonblocking: bool = false,
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// mode: Mode = default_mode
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// }
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//
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// Question:
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// - what should you do if you want to also read the file after opening it?
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// - go to the documentation of the struct `std.Io.Dir` here:
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// https://ziglang.org/documentation/master/std/#std.Io.Dir
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// - can you find a function for opening a file? how about deleting a file?
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// - what kind of options can you use with those functions?
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