Absolute path to 'ifconfig' is '/sbin/ifconfig', so running it may require superuser privileges (eg. root).
secretdk@linux-1bnb:~> /sbin/ifconfig
eth0      Link encap:Ethernet  HWaddr 00:03:FF:69:CD:41
          inet addr:145.118.6.50  Bcast:145.118.6.127  Mask:255.255.255.128
          inet6 addr: fe80::203:ffff:fe69:cd41/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1208 errors:0 dropped:0 overruns:0 frame:0
          TX packets:630 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1276755 (1.2 Mb)  TX bytes:65676 (64.1 Kb)
          Interrupt:11 Base address:0xec00

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:80 errors:0 dropped:0 overruns:0 frame:0
          TX packets:80 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:4936 (4.8 Kb)  TX bytes:4936 (4.8 Kb)