Getting IP address of the beagleboard using python

问题:

SIOCGIFADDR = 0x8915

def getIpAddr(iface = 'eth0'):

     ifreq = struct.pack('16sH14s', iface, socket.AF_INET, '\x00'*14)
     try:
         res = fcntl.ioctl(sock, SIOCGIFADDR, ifreq)
     except:
         return None   
     ip = struct.unpack('16sH2x4s8x', res)[2]
     return socket.inet_ntoa(ip)

At each step what are the return values of the functions? And, what is SIOCGIFADDR? Also, why [2] has been used following the unpack() function?

回答1:

SIOCGIFADDR : is stands for get internet interface address means 'eth0'. This is CPU macro which is written at address 0x8915. You cant take access of that cpu address so you have to go through pack and unpack function using parameters "16sH2x4s8x" IP address which u want from machine it have 4 fields like "192.168.5.20" so that (4*4) 16 is required likewise search more fields of pack unpack functions.