HOWTO: Retrieve Current User and Domain Names on Windows

Sample Code

#include <windows.h>
#include <stdlib.h>
#include <string.h>
#include <netcons.h>
#include <wksta.h>
#include <neterr.h>

//**********************************************************************
// 
//  FUNCTION:     GetCurrentUserAndDomain - This function looks up
//                the user name and domain name for the user account
//                associated with the calling thread.
// 
//  PARAMETERS:   szUser - a buffer that receives the user name
//                pcchUser - the size, in characters, of szUser
//                szDomain - a buffer that receives the domain name
//                pcchDomain - the size, in characters, of szDomain
// 
//  RETURN VALUE: NERR_Success if the function succeeds. Otherwise, the
//                function returns a network error code from neterr.h.
// 
//                If either of the supplied buffers are too small, the
//                function will return NERR_BufTooSmall and pcchUser and
//                pcchDomain will be adjusted to reflect the required
//                buffer sizes.
// 
//**********************************************************************

unsigned short GetCurrentUserAndDomain(char* szUser, int* pcchUser, 
      char* szDomain, int* pcchDomain) {

   unsigned short iNetErr;

   struct wksta_info_10 far* pwi10 = NULL;
   unsigned short cbwi10 = 0;

   int iDomainLen;
   int iUserLen;

   // Obtain the required buffer size for the account information.
   iNetErr = NetWkstaGetInfo(NULL, 10, (char far*) pwi10, cbwi10,
         &cbwi10);

   // Call should have failed due to zero-length buffer.
   if (iNetErr != NERR_BufTooSmall)
      return iNetErr;

   // Allocate buffer for account information.
   pwi10 = (struct wksta_info_10 far*) malloc(cbwi10);
   if (pwi10 == NULL)
      return NERR_ProgNeedsExtraMem;

   // Retrieve the account information.
   iNetErr = NetWkstaGetInfo(NULL, 10, (char far*) pwi10, cbwi10,
         &cbwi10);
   if (iNetErr == NERR_Success) {

      // If possible, copy the user name to the supplied buffer.
      iUserLen = strlen(pwi10->wki10_username) + 1;
      if (iUserLen < *pcchUser)
         strcpy(szUser, pwi10->wki10_username);
      else 
         iNetErr = NERR_BufTooSmall;

      // Set required buffer size.
      *pcchUser = iUserLen;

      // if possible, copy the domain name to the supplied buffer.
      iDomainLen = strlen(pwi10->wki10_logon_domain) + 1;
      if (iDomainLen < *pcchDomain)
         strcpy(szDomain, pwi10->wki10_logon_domain);
      else
         iNetErr = NERR_BufTooSmall;

      // Set required buffer size.
      *pcchDomain = iDomainLen;
   }

   // Free the allocated buffer.
   free(pwi10);

   return iNetErr;
}