C# Signature:

[DllImport("userenv.dll", SetLastError=true, CharSet=CharSet.Auto)]
static extern bool GetProfilesDirectory(StringBuilder path, ref int size);

Sample Code:

   StringBuilder path = new StringBuilder(4*1024);
   int size = path.Capacity;
   if (GetProfilesDirectory(path, ref size) )
   {
       ... use path value, size contains length...
   }

Sample code using gcc in Cygwin as a GUI w/ ICON executable

// GUI + ICON:

// copy bfe.ico to cwd

// echo 'this icon bfe.ico' > this.rc

// windres this.rc O coff o this.res

// gcc Wall -Wl,--enable-stdcall-fixup -mnop-fun-dllimport mwindows +

// this.res usrprof.c /.s32/userenv.dll

// https://cygwin.com/cygwin-ug-net/using.html

// https://cygwin.com/cygwin-ug-net/using.html

// use gcc to compile

// gcc Wall -Wl,--enable-stdcall-fixup -mnop-fundllimport pleaz.c

// the default during compilation is to produce a console application.

// If you are writing a GUI program, you should either compile with

// mwindows as explained above, or add the string "-Wl,-subsystem,windows"

// to the GCC command line.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <windows.h>
#include <w32api/windows.h>
#include <w32api/userenv.h>

int main() {
    DWORD size = 4*1024;
    char *path = malloc(size);
    if (GetProfilesDirectory(path, &size) ) {
        printf("%d %s\n", (int)size, path);
        MessageBox(NULL, path, "GetProfilesDirectory()", MB_OK);
    }
    return 0;
}

Contributed by John Refling