Getting path relative to the current working directory

Question

I m writing a console utility to do some processing on files specified on the commandline  but I ve run into a problem I can t solve through Google Stack nbsp Overflow  If a full path  including drive letter  is specified  how do I reformat that path to be relative to the current working directory     There must be something similar to the VirtualPathUtility MakeRelative function  but if there is  it eludes me

User · Answer

You can use Environment CurrentDirectory to get the current directory  and FileSystemInfo FullPath to get the full path to any location  So  fully qualify both the current directory and the file in question  and then check whether the full file name starts with the directory name - if it does  just take the appropriate substring based on the directory name s length   Here s some sample code   using System  using System IO   class Program       public static void Main string   args                string currentDir   Environment CurrentDirectory          DirectoryInfo directory   new DirectoryInfo currentDir           FileInfo file   new FileInfo args 0             string fullDirectory   directory FullName          string fullFile   file FullName           if   fullFile StartsWith fullDirectory                         Console WriteLine  Unable to make relative path                      else                          The  1 is to avoid the directory separator             Console WriteLine  Relative path   0                                  fullFile Substring fullDirectory Length 1                        I m not saying it s the most robust thing in the world  symlinks could probably confuse it  but it s probably okay if this is just a tool you ll be using occasionally

User · Answer

There is also a way to do this with some restrictions  This is the code from the article   public string RelativePath string absPath  string relTo                string   absDirs   absPath Split                string   relDirs   relTo Split                   Get the shortest of the two paths          int len   absDirs Length  lt  relDirs Length   absDirs Length   relDirs Length             Use to determine where in the loop we exited          int lastCommonRoot   -1  int index             Find common root          for  index   0  index  lt  len  index                          if  absDirs index     relDirs index                   lastCommonRoot   index              else break                       If we didn t find a common prefix then throw          if  lastCommonRoot    -1                        throw new ArgumentException  Paths do not have a common base                         Build up the relative path          StringBuilder relativePath   new StringBuilder               Add on the             for  index   lastCommonRoot   1  index  lt  absDirs Length  index                          if  absDirs index  Length  gt  0  relativePath Append                               Add on the folders          for  index   lastCommonRoot   1  index  lt  relDirs Length - 1  index                          relativePath Append relDirs index                             relativePath Append relDirs relDirs Length - 1            return relativePath ToString            When executing this piece of code   string path1     C  Inetpub wwwroot Project1 Master Dev SubDir1    string path2     C  Inetpub wwwroot Project1 Master Dev SubDir2 SubDirIWant    System Console WriteLine  RelativePath path1  path2    System Console WriteLine  RelativePath path2  path1      it prints out      SubDir2 SubDirIWant       SubDir1

User · Answer

public string MakeRelativePath string workingDirectory  string fullPath        string result   string Empty      int offset          this is the easy case   The file is inside of the working directory      if  fullPath StartsWith workingDirectory                  return fullPath Substring workingDirectory Length   1                 the hard case has to back out of the working directory     string   baseDirs   workingDirectory Split new char                            string   fileDirs   fullPath Split new char                                if we failed to split  empty strings   or the drive letter does not match     if  baseDirs Length  lt   0    fileDirs Length  lt   0    baseDirs 0     fileDirs 0                     can t create a relative path between separate harddrives partitions          return fullPath                skip all leading directories that match     for  offset   1  offset  lt  baseDirs Length  offset                  if  baseDirs offset     fileDirs offset               break                back out of the working directory     for  int i   0  i  lt   baseDirs Length - offset   i                  result                          step into the file path     for  int i   offset  i  lt  fileDirs Length-1  i                  result    fileDirs i                        append the file     result    fileDirs fileDirs Length - 1        return result      This code is probably not bullet-proof but this is what I came up with   It s a little more robust   It takes two paths and returns path B as relative to path A   example   MakeRelativePath  c   dev  foo  bar    c   dev  junk  readme txt     returns           junk  readme txt   MakeRelativePath  c   dev  foo  bar    c   dev  foo  bar  docs  readme txt     returns   docs  readme txt

User · Answer

Thanks to the other answers here and after some experimentation I ve created some very useful extension methods   public static string GetRelativePathFrom this FileSystemInfo to  FileSystemInfo from        return from GetRelativePathTo to      public static string GetRelativePathTo this FileSystemInfo from  FileSystemInfo to        Func lt FileSystemInfo  string gt  getPath   fsi   gt                var d   fsi as DirectoryInfo          return d    null   fsi FullName   d FullName TrimEnd                           var fromPath   getPath from       var toPath   getPath to        var fromUri   new Uri fromPath       var toUri   new Uri toPath        var relativeUri   fromUri MakeRelativeUri toUri       var relativePath   Uri UnescapeDataString relativeUri ToString          return relativePath Replace      Path DirectorySeparatorChar       Important points    Use FileInfo and DirectoryInfo as method parameters so there is no ambiguity as to what is being worked with  Uri MakeRelativeUri expects directories to end with a trailing slash  DirectoryInfo FullName doesn t normalize the trailing slash  It outputs whatever path was used in the constructor  This extension method takes care of that for you

User · Answer

If you don t mind the slashes being switched  you could  ab use Uri   Uri file   new Uri   c  foo bar blop blap txt       Must end in a slash to indicate folder Uri folder   new Uri   c  foo bar     string relativePath    Uri UnescapeDataString      folder MakeRelativeUri file           ToString            Replace      Path DirectorySeparatorChar           As a function method   string GetRelativePath string filespec  string folder        Uri pathUri   new Uri filespec          Folders must end in a slash     if   folder EndsWith Path DirectorySeparatorChar ToString                   folder    Path DirectorySeparatorChar            Uri folderUri   new Uri folder       return Uri UnescapeDataString folderUri MakeRelativeUri pathUri  ToString   Replace      Path DirectorySeparatorChar

[c#] Getting path relative to the current working directory?

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