Getting System Information

The following example uses the GetComputerName, GetUserName, GetSystemDirectory, GetWindowsDirectory, and ExpandEnvironmentStrings functions to get information that describes the system configuration.

#include <windows.h>
#include <tchar.h>
#include <stdio.h>

const TCHAR* envVarStrings[] =
{
 TEXT("OS = %OS%"),
 TEXT("PATH = %PATH%"),
 TEXT("HOMEPATH = %HOMEPATH%"),
 TEXT("TEMP = %TEMP%")
};
#define ENV_VAR_STRING_COUNT (sizeof(envVarStrings)/sizeof(TCHAR*))
#define INFO_BUFFER_SIZE 32767
TCHAR infoBuf[INFO_BUFFER_SIZE] = {'\0'};
void printError(const TCHAR* msg );

void main( )
{
 DWORD i = 0;
 DWORD bufCharCount = INFO_BUFFER_SIZE;
 
 // Get and display the name of the computer.
 if( !::GetComputerName( infoBuf, &bufCharCount ) )
 printError( TEXT("GetComputerName") ); 
 _tprintf( TEXT("\nComputer name: %s"), infoBuf ); 
 
 // Get and display the user name. 
 bufCharCount = INFO_BUFFER_SIZE;
 if( !::GetUserName( infoBuf, &bufCharCount ) )
 printError( TEXT("GetUserName") ); 
 _tprintf( TEXT("\nUser name: %s"), infoBuf ); 
 
 // Get and display the system directory. 
 if( !::GetSystemDirectory( infoBuf, INFO_BUFFER_SIZE ) )
 printError( TEXT("GetSystemDirectory") ); 
 _tprintf( TEXT("\nSystem Directory: %s"), infoBuf ); 
 
 // Get and display the Windows directory. 
 if( !::GetWindowsDirectory( infoBuf, INFO_BUFFER_SIZE ) )
 printError( TEXT("GetWindowsDirectory") ); 
 _tprintf( TEXT("\nWindows Directory: %s"), infoBuf ); 
 
 // Expand and display a few environment variables. 
 _tprintf( TEXT("\n\nSmall selection of Environment Variables:") ); 
 for( i = 0; i < ENV_VAR_STRING_COUNT; ++i )
 {
 bufCharCount = ::ExpandEnvironmentStrings(envVarStrings[i], infoBuf,
 INFO_BUFFER_SIZE ); 
 if( bufCharCount > INFO_BUFFER_SIZE )
 _tprintf( TEXT("\n\t(Buffer too small to expand: \"%s\")"), 
 envVarStrings[i] );
 else if( !bufCharCount )
 printError( TEXT("ExpandEnvironmentStrings") );
 else
 _tprintf( TEXT("\n %s"), infoBuf );
 }
 _tprintf( TEXT("\n\n"));
}

void printError(const TCHAR* msg )
{
 TCHAR sysMsg[MAX_PATH] = {'\0'};
 TCHAR* p = sysMsg;
 DWORD eNum = ::GetLastError();

 ::FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM | 
 FORMAT_MESSAGE_IGNORE_INSERTS,
 nullptr, eNum,
 MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
 sysMsg, MAX_PATH, nullptr );

 // Trim the end of the line and terminate it with a null
 // 9 - \t (horizontal tab)
 // [0 - 32) - All characters in this area excepting 9
 // 46 - . (dot)
 while (*p++)
 {
 if ((*p != 9 && *p < 32) || *p == 46)
 {
 *p = 0;
 break;
 }
 }	

 // Display the message
 _tprintf( TEXT("\n\t%s failed with error %d (%s)"), msg, eNum, sysMsg );

 p = nullptr;
}