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Best way to extract mac address from ifconfig output ?

Answer 1

+2 A:

Not sure whether there really are any advantages, but you can simply use awk:

ifconfig eth0 | awk '/HWaddr/ {print $5}'

albertb 2008-10-29 05:55:18

Answer 2

+7 A:

I would use:

ifconfig eth0 | grep -o -E '([[:xdigit:]]{1,2}:){5}[[:xdigit:]]{1,2}'

The -o will cause grep to only print the part of the line that matches the expression. [[:xdigit:]]{1,2} will match 1 or 2 hexidecimal digits (Solaris doesn't output leading zeros).

Robert Gamble 2008-10-29 05:56:42

What? This will match regardless of placement of the MAC address whereas the other solutions will not.

Robert Gamble 2008-10-29 06:04:07

It does have the advantage of also working on OSX since that ifconfig use 'ether' instead of 'HWaddr'

albertb 2008-10-29 06:07:34

That was my intention, I have worked with plenty of different Unixes and this is the only solution that will work on all of them.

Robert Gamble 2008-10-29 06:10:22

+1 for searching for the string you WANT, rather than the "noise" surrounding it.

Adam Liss 2008-10-29 06:10:27

Why the downvote?

Robert Gamble 2008-10-29 06:44:57

I don't understand the downvote, my original thought was that it's over-engineered for the job but it works and is better on slightly different output (I'd want to put it in a script so I don't have to remember the regex).

paxdiablo 2008-10-29 06:51:27

That 'grep -o' is a handy addition to my knowledge as well.

paxdiablo 2008-10-29 06:53:11

Are there any UNICES that don't output leading zeros for the MAC sections (necessitating "{1,2}" instead of "{2}")?

paxdiablo 2008-10-29 06:57:23

@Pax, actually yes, I think Solaris does this, I'll update.

Robert Gamble 2008-10-29 12:14:25

Answer 3

+3 A:

I like using /sbin/ip for these kind of tasks, because it is far easier to parse:

$ ip link show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0c:29:30:21:48 brd ff:ff:ff:ff:ff:ff

You can trivially get the mac address from this output with awk:

$ ip link show eth0 | awk '/ether/ {print $2}'
00:0c:29:30:21:48

If you want to put a little more effort in, and parse more data out, I recommend using the -online argument to the ip command, which will let you treat every line as a new device:

$ ip -o link 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue \    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000\    link/ether 00:0c:29:30:21:48 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000\    link/ether 00:0c:29:30:21:52 brd ff:ff:ff:ff:ff:ff
4: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 100\    link/[65534] 
5: sit0: <NOARP> mtu 1480 qdisc noop \    link/sit 0.0.0.0 brd 0.0.0.0

Jerub 2008-10-29 11:58:40

Not all distros ship `/sbin/ip`, which belongs to the `iproute2` package. But this is the best solution: ip is much nicer than ifconfig!

ephemient 2008-10-29 14:30:23

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Best way to extract mac address from ifconfig output ?

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