#判断命令是否存在

function cmd_exists() {

   local ret='0'

   command -v $1 >/dev/null 2>&1 || { local ret='1'; }

   # fail on non-zero return value

   if [ "$ret" -ne 0 ]; then

       return 1

   fi

       return 0

}

#检查是否安装telnet

if $(cmd_exists telnet);then

       echo "telnet found"

else

       echo "telnet not found,please install telnet!"

       exit 1

fi