cat.zig

const std = @import("std");
const File = std.os.File;

fn copyFile(src: File, dst: File) !void {
    var buf = []u8 {0} ** 1024;
    while (true) {
        const n = try src.read(&buf);
        if (n == 0) break;
        try dst.write(buf[0..n]);
    }
}

pub fn main() !void {
    const stdout = try std.io.getStdOut();

    var direct_allocator = std.heap.DirectAllocator.init();
    defer direct_allocator.deinit();

    var arena = std.heap.ArenaAllocator.init(&direct_allocator.allocator);
    defer arena.deinit();

    var argsIter = std.os.args();
    const programName = try argsIter.next(&arena.allocator) orelse return;

    var fileName = try (argsIter.next(&arena.allocator) orelse {
        const stdin = try std.io.getStdIn();
        try copyFile(stdin, stdout);
        return;
    });

    while (true) {
        const file = try File.openRead(fileName);
        defer file.close();
        try copyFile(file, stdout);
        fileName = try (argsIter.next(&arena.allocator) orelse break);
    }
}