如何使用Vala读取root拥有的文件夹？

Question

我试图读取路径/var/cache/apt/archives具有下列权限：

drwxr-xr-x 3 root root 90112 ago 2 14:36 archives 

而且我得到了以下错误：

ERROR: Error opening directory '/var/cache/apt/archives/partial': Permission denied 

有人能帮我个忙？

的源代码如下：

using Gtk; 
using GLib; 

private int64[] get_folder_data (File file, string space = "",  Cancellable? cancellable = null) throws Error 
{ 
    FileEnumerator enumerator = file.enumerate_children (
    "standard::*", 
    FileQueryInfoFlags.NOFOLLOW_SYMLINKS, 
    cancellable); 

    int64 files = 0; 
    int64 size = 0; 
    int64[] data = new int64[2]; 
    FileInfo info = null; 

    while (cancellable.is_cancelled() == false && ((info = enumerator.next_file (cancellable)) != null)) { 
     if (info.get_file_type() == FileType.DIRECTORY) { 
      File subdir = file.resolve_relative_path (info.get_name()); 
      get_folder_data (subdir, space + " ", cancellable); 
     } else { 
      files += 1;//Sum Files 
      size += info.get_size();//Accumulates Size 
     } 
    } 

    if (cancellable.is_cancelled()) { 
     throw new IOError.CANCELLED ("Operation was cancelled"); 
    } 

    data[0] = files; 
    data[1] = size; 

    stdout.printf ("APT CACHE SIZE: %s\n", files.to_string()); 
    stdout.printf ("APT CACHE FILES: %s\n", size.to_string()); 

    return data; 
} 

public static int main (string[] args) { 
    Gtk.init (ref args); 

    File APT_CACHE_PATH = File.new_for_path ("/var/cache/apt/archives"); 
    try { 
     get_folder_data (APT_CACHE_PATH, "", new Cancellable()); 
    } catch (Error e) { 
     stdout.printf ("ERROR: %s\n", e.message);  
    } 
    Gtk.main(); 
    return 0; 
} 

而且我用的编译的命令如下：

valac --pkg gtk+-3.0 --pkg glib-2.0 --pkg gio-2.0 apt-cache.vala 

Answer 1

如果你运行你的应用程序作为一个普通用户，你必须排除“部分”目录，它具有更多限制性权限（0700）：

drwx------ 2 _apt root 4096 Jul 29 11:36 /var/cache/apt/archives/partial 

一种排除标准TiAl基dir是只是忽略任何目录不可访问：

int64[] data = new int64[2]; 
FileEnumerator enumerator = null; 
try { 
    enumerator = file.enumerate_children (
     "standard::*", 
     FileQueryInfoFlags.NOFOLLOW_SYMLINKS, 
     cancellable); 
} 
catch (IOError e) { 
    stderr.printf ("WARNING: Unable to get size of dir '%s': %s\n", file.get_path(), e.message); 
    data[0] = 0; 
    data[1] = 0; 
    return data; 
} 

此外，它可能是一个好主意，总是明确地忽略了部分文件夹。

如果您打算让您的实用程序对root用户有用，您甚至可以考虑添加一个命令行选项，如“--include-partial-dir”。

同样的事情可以用简单的bash命令来完成，这比编写自己的程序容易得多。

du -sh /var/cache/apt/archives 
find /var/cache/apt/archives -type f | wc -l 

注意du和find也警告人迹罕至的部分目录：

$ du -sh /var/cache/apt/archives 
du: cannot read directory '/var/cache/apt/archives/partial': Permission denied 
4.6G /var/cache/apt/archives 

$ find /var/cache/apt/archives -type f | wc -l 
find: '/var/cache/apt/archives/partial': Permission denied 
3732