country=GB
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
    ssid="wifi_name"
    psk="wifi_password"
}

# The loopback network interface
auto lo
iface lo inet loopback

# The primary (wired) network interface
iface eth0 inet dhcp

# The wifi (wireless) network interface
auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
        wpa-ssid "wifi_name"
        wpa-psk "wifi_password"

pi@rpi3:~ $ iwconfig
lo        no wireless extensions.

wlan0     IEEE 802.11  ESSID:off/any
          Mode:Managed  Access Point: Not-Associated   Tx-Power=31 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on

eth0      no wireless extensions.

pi@rpi3:~ $ ifconfig -a
eth0      Link encap:Ethernet  HWaddr ____
          inet addr:192.168.0.14  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: _____ Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1874 errors:0 dropped:2 overruns:0 frame:0
          TX packets:162 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:95269 (93.0 KiB)  TX bytes:21921 (21.4 KiB)

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:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

wlan0     Link encap:Ethernet  HWaddr ____
          inet6 addr: _____ Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:12 errors:0 dropped:0 overruns:0 frame:0
          TX packets:23 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1188 (1.1 KiB)  TX bytes:3422 (3.3 KiB)