DirectoryInfo.EnumerateFiles(...) 导致 UnauthorizedAccessException(和其他异常) [英] DirectoryInfo.EnumerateFiles(...) causes UnauthorizedAccessException (and other exceptions)

问题描述

我最近需要枚举整个文件系统以查找特定类型的文件以进行审计.由于对要扫描的文件系统的权限有限，这导致我遇到了几个异常.其中，最流行的是 UnauthorizedAccessException 对我来说很重要懊恼，PathTooLongException.

I have recently had a need to Enumerate an entire file system looking for specific types of files for auditing purposes. This has caused me to run into several exceptions due to having limited permissions on the file system to be scanned. Among them, the most prevalent have been UnauthorizedAccessException and much to my chagrin, PathTooLongException.

这些通常不会成为问题，只是它们会使 IEnumerable 无效，从而阻止我完成扫描.

These would not normally be an issue except that they invalidate the IEnumerable, preventing me from being able to complete the scan.

推荐答案

为了解决这个问题，我创建了一个替代的 File System Enumerator.尽管它可能并不完美，但它执行得相当快，并捕获了我遇到的两个异常.它将找到与传递给它的搜索模式匹配的任何目录或文件.

In order to solve this problem, I have created a replacement File System Enumerator. Although it may not be perfect, it performs fairly quickly and traps the two exceptions that I have run into. It will find any directories or files that match the search pattern passed to it.

// This code is public domain
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using log4net;

public class FileSystemEnumerable : IEnumerable<FileSystemInfo>
{
    private ILog _logger = LogManager.GetLogger(typeof(FileSystemEnumerable));

    private readonly DirectoryInfo _root;
    private readonly IList<string> _patterns;
    private readonly SearchOption _option;

    public FileSystemEnumerable(DirectoryInfo root, string pattern, SearchOption option)
    {
        _root = root;
        _patterns = new List<string> { pattern };
        _option = option;
    }

    public FileSystemEnumerable(DirectoryInfo root, IList<string> patterns, SearchOption option)
    {
        _root = root;
        _patterns = patterns;
        _option = option;
    }

    public IEnumerator<FileSystemInfo> GetEnumerator()
    {
        if (_root == null || !_root.Exists) yield break;

        IEnumerable<FileSystemInfo> matches = new List<FileSystemInfo>();
        try
        {
            _logger.DebugFormat("Attempting to enumerate '{0}'", _root.FullName);
            foreach (var pattern in _patterns)
            {
                _logger.DebugFormat("Using pattern '{0}'", pattern);
                matches = matches.Concat(_root.EnumerateDirectories(pattern, SearchOption.TopDirectoryOnly))
                                 .Concat(_root.EnumerateFiles(pattern, SearchOption.TopDirectoryOnly));
            }
        }
        catch (UnauthorizedAccessException)
        {
            _logger.WarnFormat("Unable to access '{0}'. Skipping...", _root.FullName);
            yield break;
        }
        catch (PathTooLongException ptle)
        {
            _logger.Warn(string.Format(@"Could not process path '{0}{1}'.", _root.Parent.FullName, _root.Name), ptle);
            yield break;
        } catch (System.IO.IOException e)
        {
            // "The symbolic link cannot be followed because its type is disabled."
            // "The specified network name is no longer available."
            _logger.Warn(string.Format(@"Could not process path (check SymlinkEvaluation rules)'{0}{1}'.", _root.Parent.FullName, _root.Name), e);
            yield break;
        }


        _logger.DebugFormat("Returning all objects that match the pattern(s) '{0}'", string.Join(",", _patterns));
        foreach (var file in matches)
        {
            yield return file;
        }

        if (_option == SearchOption.AllDirectories)
        {
            _logger.DebugFormat("Enumerating all child directories.");
            foreach (var dir in _root.EnumerateDirectories("*", SearchOption.TopDirectoryOnly))
            {
                _logger.DebugFormat("Enumerating '{0}'", dir.FullName);
                var fileSystemInfos = new FileSystemEnumerable(dir, _patterns, _option);
                foreach (var match in fileSystemInfos)
                {
                    yield return match;
                }
            }
        }
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}

用法相当简单.

//This code is public domain
var root = new DirectoryInfo(@"c:wherever");
var searchPattern = @"*.txt";
var searchOption = SearchOption.AllDirectories;
var enumerable = new FileSystemEnumerable(root, searchPattern, searchOption);

如果人们觉得它有用，可以自由使用它.

People are free to use it if they find it useful.

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