PrintEnvironmentVariable

功能：打印系统指定环境变量的值

来源：《Windows核心编程（第五版）》第4.1.4 进程的环境变量

在主程序中只要调用以下代码：

PrintEnvironmentVariable (TEXT("TEMP"));

代码：

void PrintEnvironmentVariable(PCTSTR pszVariableName)
{
       PTSTR  pszValue = NULL;
       //Get the size of thebuffer that is required to store the value
       DWORD dwRusult = GetEnvironmentVariable(pszVariableName, pszValue, 0);
       if (dwRusult != 0)
       {
              //Allocate the buffer to store the environment variable value
              DWORD size = dwRusult * sizeof(TCHAR);
              pszValue = (PTSTR)malloc(size);
              GetEnvironmentVariable(pszVariableName, pszValue, size);
              _tprintf(TEXT("%s=%s\n"), pszVariableName, pszValue);
              free (pszValue);
       }else
       {
              _tprintf(TEXT("'%s'=<unknow value>\n"), pszVariableName);
       }
}