fileHardLink

fn fileHardLink(
    userdata: ?*anyopaque,
    file: File,
    new_dir: Dir,
    new_sub_path: []const u8,
    options: File.HardLinkOptions,
) File.HardLinkError!void {
    _ = userdata;
    if (native_os != .linux) return error.OperationUnsupported;

    var new_path_buffer: [posix.PATH_MAX]u8 = undefined;
    const new_sub_path_posix = try pathToPosix(new_sub_path, &new_path_buffer);

    const flags: u32 = if (options.follow_symlinks)
        posix.AT.SYMLINK_FOLLOW | posix.AT.EMPTY_PATH
    else
        posix.AT.EMPTY_PATH;

    return linkat(file.handle, "", new_dir.handle, new_sub_path_posix, flags) catch |err| switch (err) {
        error.FileNotFound => {
            if (options.follow_symlinks) return error.FileNotFound;
            var proc_buf: ["/proc/self/fd/-2147483648\x00".len]u8 = undefined;
            const proc_path = std.mem.printSentinel(&proc_buf, "/proc/self/fd/{d}", .{file.handle}, 0) catch
                unreachable;
            return linkat(posix.AT.FDCWD, proc_path, new_dir.handle, new_sub_path_posix, posix.AT.SYMLINK_FOLLOW);
        },
        else => |e| return e,
    };
}