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：

1 PrintEnvironmentVariable (TEXT("TEMP"));

代码：

 1 void PrintEnvironmentVariable(PCTSTR pszVariableName)
 2 {
 3        PTSTR  pszValue = NULL;
 4        //Get the size of thebuffer that is required to store the value
 5        DWORD dwRusult = GetEnvironmentVariable(pszVariableName, pszValue, 0);
 6        if (dwRusult != 0)
 7        {
 8               //Allocate the buffer to store the environment variable value
 9               DWORD size = dwRusult * sizeof(TCHAR);
10               pszValue = (PTSTR)malloc(size);
11               GetEnvironmentVariable(pszVariableName, pszValue, size);
12               _tprintf(TEXT("%s=%s\n"), pszVariableName, pszValue);
13               free (pszValue);
14        }else
15        {
16               _tprintf(TEXT("'%s'=<unknow value>\n"), pszVariableName);
17        }
18 }