7

Is there a Windows API function to extract the drive letter from a Windows path such as

U:\path\to\file.txt
\\?\U:\path\to\file.txt

while correctly sorting out 

relative\path\to\file.txt:alternate-stream

etc?

Felix Dombek
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4 Answers4

13

PathGetDriveNumber returns 0 through 25 (corresponding to 'A' through 'Z') if the path has a drive letter, or -1 otherwise.

cprogrammer
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4

Here is code that combines the accepted answer (thanks!) with PathBuildRoot to round out the solution

#include <Shlwapi.h>    // PathGetDriveNumber, PathBuildRoot
#pragma comment(lib, "Shlwapi.lib")

/** Returns the root drive of the specified file path, or empty string on error */
std::wstring GetRootDriveOfFilePath(const std::wstring &filePath)
{
// get drive #      http://msdn.microsoft.com/en-us/library/windows/desktop/bb773612(v=vs.85).aspx
int drvNbr = PathGetDriveNumber(filePath.c_str());

if (drvNbr == -1)   // fn returns -1 on error
    return L"";

wchar_t buff[4] = {};   // temp buffer for root 

// Turn drive number into root      http://msdn.microsoft.com/en-us/library/bb773567(v=vs.85)
PathBuildRoot(buff,drvNbr);

return std::wstring(buff);  
}
Tom
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  • Thanks - two comments: you don't need to copy the array pointer, just use the array itself as the parameter to `PathBuildRoot`. And, if you want to initialize a static array, just use `= {}` because this is the general solution and works for all types and sizes. – Felix Dombek Jun 16 '12 at 13:28
  • @FelixDombek: fixed, thanks! This is cleaner, I like it. I'm still fairly new to C++, your feedback is appreciated – Tom Jun 18 '12 at 00:27
  • That's cool. Then you might be interested to know that you can (almost) always use `buff` to mean the same thing as `&buff[0]` for static arrays. Works for function calls, returns, etc. (see http://www.lysator.liu.se/c/c-faq/c-2.html, arrays decay into pointers in expressions **except** when the array is the operand of a `sizeof` or `&` operator which is not the case here) – Felix Dombek Jun 18 '12 at 15:59
3

Depending on your requirements, you might also want to consider GetVolumePathName to get the mount point, which may or may not be a drive letter.

Peter Tseng
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0
#include <iostream>
#include <string>

using namespace std;

int main()
{    
    string aux;
    cin >> aux;
    int pos = aux.find(':', 0);
    cout << aux.substr(pos-1,1) << endl;
    return 0;
}
m0skit0
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