PathRelativePathToA function (shlwapi.h)

Article
02/09/2023

Creates a relative path from one file or folder to another.

Syntax

BOOL PathRelativePathToA(
  [out] LPSTR  pszPath,
  [in]  LPCSTR pszFrom,
  [in]  DWORD  dwAttrFrom,
  [in]  LPCSTR pszTo,
  [in]  DWORD  dwAttrTo
);

Parameters

[out] pszPath

Type: LPTSTR

A pointer to a string that receives the relative path. This buffer must be at least MAX_PATH characters in size.

[in] pszFrom

Type: LPCTSTR

A pointer to a null-terminated string of maximum length MAX_PATH that contains the path that defines the start of the relative path.

[in] dwAttrFrom

Type: DWORD

The file attributes of pszFrom. If this value contains FILE_ATTRIBUTE_DIRECTORY, pszFrom is assumed to be a directory; otherwise, pszFrom is assumed to be a file.

[in] pszTo

Type: LPCTSTR

A pointer to a null-terminated string of maximum length MAX_PATH that contains the path that defines the endpoint of the relative path.

[in] dwAttrTo

Type: DWORD

The file attributes of pszTo. If this value contains FILE_ATTRIBUTE_DIRECTORY, pszTo is assumed to be directory; otherwise, pszTo is assumed to be a file.

Return value

Type: BOOL

Returns TRUE if successful, or FALSE otherwise.

Remarks

This function takes a pair of paths and generates a relative path from one to the other. The paths do not have to be fully qualified, but they must have a common prefix, or the function will fail and return FALSE.

For example, let the starting point, pszFrom, be "c:\FolderA\FolderB\FolderC", and the ending point, pszTo, be "c:\FolderA\FolderD\FolderE". PathRelativePathTo will return the relative path from pszFrom to pszTo as: "....\FolderD\FolderE". You will get the same result if you set pszFrom to "\FolderA\FolderB\FolderC" and pszTo to "\FolderA\FolderD\FolderE". On the other hand, "c:\FolderA\FolderB" and "a:\FolderA\FolderD do not share a common prefix, and the function will fail. Note that "\" is not considered a prefix and is ignored. If you set pszFrom to "\FolderA\FolderB", and pszTo to "\FolderC\FolderD", the function will fail.

Examples

#include <windows.h>
#include <iostream.h>
#include "Shlwapi.h"

void main(void)
{
    char szOut[MAX_PATH] = "";
    char szFrom[ ] = "c:\\a\\b\\path";
    char szTo[ ] = "c:\\a\\x\\y\\file";

    cout  <<  "The relative path is relative from: ";
    cout  <<  szFrom;
    cout  <<  "\n";

    cout  <<  "The relative path is relative to: ";
    cout  <<  szTo;
    cout  <<  "\n";

    PathRelativePathTo(szOut,
                       szFrom,
                       FILE_ATTRIBUTE_DIRECTORY,
                       szTo,
                       FILE_ATTRIBUTE_NORMAL);

    cout  <<  "The relative path is: ";
    cout  <<  szOut;
    cout  <<  "\n";
}

OUTPUT:
==================
The relative path is relative from: c:\a\b\path
The relative path is relative to: c:\a\x\y\file
The relative path is: ..\..\x\y\file

Note

The shlwapi.h header defines PathRelativePathTo as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional, Windows XP [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	shlwapi.h
Library	Shlwapi.lib
DLL	Shlwapi.dll (version 4.71 or later)

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