net_iface.py

#!/usr/bin/env python
# show network interfaces
# like ifconfig
# this is for a linux box


import sys
import socket
import fcntl
import struct
import array

SIOCGIFCONF = 0x8912    # from C library sockios.h
STRUCT_SIZE_32 = 32
STRUCT_SIZE_64 = 40
PLATFORM_32_MAX_NUMBER = 2**32
DEFAULT_INTERFACES = 8


def list_interfaces():
    interfaces = []
    max_interfaces = DEFAULT_INTERFACES
    is_64bits = sys.maxsize > PLATFORM_32_MAX_NUMBER
    struct_size = STRUCT_SIZE_64 if is_64bits else STRUCT_SIZE_32
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    while True:
        bytes = max_interfaces * struct_size
        interface_names = array.array('B', '\0' * bytes)
        sock_info = fcntl.ioctl(
            sock.fileno(),
            SIOCGIFCONF,
            struct.pack('iL', bytes,interface_names.buffer_info() [0])
        )
        outbytes = struct.unpack('iL', sock_info) [0]
        if outbytes == bytes:
            max_interfaces *= 2
        else:
            break
    namestr = interface_names.tostring()
    for i in range(0, outbytes, struct_size):
        interfaces.append((namestr[i:i+16].split('\0', 1)[0]))
        return interfaces

if __name__ == '__main__':
    interfaces = list_interfaces()
    print "This machine has %s network interfaces: %s." %(len(interfaces), interface)