一个GSM的demo程序， GsmToolmanage.c等待命令和解析命令并且向GSM模块发送相应的AT指令，GsmTool_API.c通过管道和 GsmToolmanage.c通信-A GSM demo program, GsmToolmanage.c waiting for command and parsing the command and to the GSM module to send the corresponding AT instruction through the pi