Bash script to retrieve name of Ethernet Network interface
In Ubuntu 16.04 I made a script to dinamically configure IP address of the wired ethernet interface based on certain parameters. Now the problem is that in my script I assume that the name is eth0, but this is not always true.. assuming that I have only one wired network interface (not necessary plugged) but I can have also a wireless interface, how can I retrieve its name (just the wired one)?
with ifconfig
command I get:
enp7s0 Link encap:Ethernet HWaddr fc:3f:db:a2:6d:46
inet addr:192.168.0.101 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::149f:3103:af2f:1ec5/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:6784 errors:0 dropped:0 overruns:0 frame:0
TX packets:7493 errors:1 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4565079 (4.5 MB) TX bytes:827825 (827.8 KB)
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:8037 errors:0 dropped:0 overruns:0 frame:0
TX packets:8037 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1
RX bytes:2261250 (2.2 MB) TX bytes:2261250 (2.2 MB)
wlp19s0 Link encap:Ethernet HWaddr c8:ff:28:93:26:32
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:180463 errors:0 dropped:0 overruns:0 frame:0
TX packets:121275 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:229823414 (229.8 MB) TX bytes:15675806 (15.6 MB)
What I want is:
enp7s0
Solution 1:
If you want to exclude interfaces like vir
, loopback
and wl
(wireless) then the following should do the trick.
ip link | awk -F: '$0 !~ "lo|vir|wl|^[^0-9]"{print $2;getline}'
Here we use colon as delimiter -F:
then check if the row $0
does not match a certain string using regular expression.
Solution 2:
Because all interfaces would displayed under /sys/class/
, such as /sys/class/net/
listing all network interfaces,
it is possible to directly use this directly search and return the exact interface name through a simple keyword like:
ls /sys/class/net | grep enp
Solution 3:
I'd use ifconfig
(bit old and deprecated) tool or ip
command. Using ip route
you are having a list of available routes. Then get only line containing default with grep
and strip the unwanted characters off the string using sed
full command goes like:
ip route | grep default | sed -e "s/^.*dev.//" -e "s/.proto.*//"
Solution 4:
Here is best solution
ip route get 8.8.8.8 | awk -- '{printf $5}'
or
echo $(ip route get 8.8.8.8 | awk -- '{printf $5}')
in bash script you can declare main_interface and use anywhere as $main_interface
main_interface=$(ip route get 8.8.8.8 | awk -- '{printf $5}')
Solution 5:
Assuming you got only one physical interface and not some wlan interface etc. The trick is to get the interfaces. Which are in /sys/class/net and then look where they go to.
find /sys/class/net ! -type d | xargs --max-args=1 realpath | awk -F\/ '/pci/{print $NF}'
If you got more interfaces you would have to grep lspci first:
lspci | awk '/Ethernet/{print $1}'
The whole thing would turn into:
pci=`lspci | awk '/Ethernet/{print $1}'`; find /sys/class/net ! -type d | xargs --max-args=1 realpath | awk -v pciid=$pci -F\/ '{if($0 ~ pciid){print $NF}}'