Change owner of a file / directory using zig

chown.zig

const c = @cImport(@cInclude("unistd.h"));
const std = @import("std");

const ChownData = struct {
    uid: c_uint,
    gid: c_uint,
    filename: [:0]const u8,
};

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

    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
    defer arena.deinit();

    const allocator = &arena.allocator;
    const args = try std.process.argsAlloc(allocator);
    defer std.process.argsFree(allocator, args);

    if (args.len != 3) {
        try stderr.print("Expected 2 arguments\n", .{});
        std.os.exit(1);
    }

    const payload = try parseArgs(args[1], args[2]);
    try stdout.print("Changing to user {d} and gid {d} on file {s}\n", .{ payload.uid, payload.gid, payload.filename }
);

    const result = c.chown(payload.filename, payload.uid, payload.gid);
    if (result == -1) {
        const err_str = switch (std.os.errno(result)) {
            1 => "permission denied",
            2 => "no such file or directory",
            else => "something I don't know",
        };
        try stderr.print("Somethin went wrong while changing permissions on file {s} ({s})\n", .{ payload.filename, er
r_str });
        std.os.exit(1);
    }
}

fn parseArgs(user_gid: [:0]const u8, filename: [:0]const u8) !ChownData {
    const delim_u8 = [_]u8{std.fs.path.delimiter};
    var it = std.mem.split(user_gid, delim_u8[0..]);
    var uid: c_uint = undefined;
    var gid: c_uint = undefined;
    if (it.next()) |uidU8| uid = try std.fmt.parseInt(c_uint, uidU8, 10);
    if (it.next()) |gidU8| gid = try std.fmt.parseInt(c_uint, gidU8, 10);

    return ChownData{ .uid = uid, .gid = gid, .filename = filename };
}