ifconfig |grep "inet addr"|cut -f 2 -d":"|cut -f 1 -d " "|head -n 1

ifconfig

eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx
          inet addr:192.168.1.100  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::226:9eff:fe60:4640/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:6100 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5840 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:5697900 (5.4 MiB)  TX bytes:917160 (895.6 KiB)
          Interrupt:17

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:8 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:480 (480.0 b)  TX bytes:480 (480.0 b)

ifconfig|grep "inet addr"  

          inet addr:192.168.1.100  Bcast:192.168.1.255  Mask:255.255.255.0
          inet addr:127.0.0.1  Mask:255.0.0.0

ifconfig |grep "inet addr"|cut -f 2 -d":"

192.168.1.100  Bcast
127.0.0.1  Mask

ifconfig |grep "inet addr"|cut -f 2 -d":"|cut -f 1 -d " "
192.168.1.100
127.0.0.1

ifconfig |grep "inet addr"|cut -f 2 -d":"|cut -f 1 -d " "|head -n 1
192.168.1.100