DirectoryInfo.EnumerateFiles(...) 导致 UnauthorizedAccessException （和其他异常）

Question

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，让我很懊恼的是PathTooLongException。

这些通常不是问题，只是它们使 IEnumerable 无效，使我无法完成扫描。

Answer 1

为了解决这个问题，我创建了一个替代文件系统枚举器。尽管它可能并不完美，但它的执行速度相当快，并捕获了我遇到的两个异常。它将查找与传递给它的搜索模式匹配的任何目录或文件。

// 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，可以免费使用它。

Answer 2

这是另一种方式，管理您自己的枚举迭代：

IEnumerator<string> errFiles=Directory.EnumerateFiles(baseDir, "_error.txt", SearchOption.AllDirectories).GetEnumerator();
while (true)
{
    try
    {
        if (!errFiles.MoveNext())
            break;
        string errFile = errFiles.Current;
        // processing
    } catch (Exception e)
    {
        log.Warn("Ignoring error finding in: " + baseDir, e);
    }
}