REGEX with grep

Anna1987 · 03-05-2013, 05:06 PM

Hello,

I have to create a grep question which shows MAC adress from ifconfig..

I did like this:
ifconfig -a | grep -E '[[:alnum:]]+:[[:alnum:]]+:+'

In my computer this command showed me MAC adresses.

But can anyone confirm me that it works correctly andin my commandthere is no errors
? or there are others solutions?

here is output:
[root@localhost grep]# ifconfig -a | grep -E '[[:alnum:]]+:[[:alnum:]]+:+'
ether 00:1b:38:1a:3a:2c txqueuelen 1000 (Ethernet)
inet6 fe80::21b:77ff:fe77:7b6e prefixlen 64 scopeid 0x20<link>
ether 00:1b:77:77:7b:6e txqueuelen 1000 (Ethernet)

thanks for your reply and any suggestion,

chrism01 · 03-05-2013, 05:15 PM

If it works for, that's fine.
On my system (using your soln) I get

Code:

br0       Link encap:Ethernet  HWaddr E0:CB:4E:B9:5F:1A  
eth0      Link encap:Ethernet  HWaddr E0:CB:4E:B9:5F:1A  
eth1      Link encap:Ethernet  HWaddr 00:02:A5:42:D0:CC  
virbr0    Link encap:Ethernet  HWaddr 52:54:00:52:23:F5  
virbr0-nic Link encap:Ethernet  HWaddr 52:54:00:52:23:F5  

# I would do it this way
ifconfig|grep HW|awk '{print $5}'
E0:CB:4E:B9:5F:1A
E0:CB:4E:B9:5F:1A
52:54:00:52:23:F5

Anna1987 · 03-06-2013, 12:18 AM

Yeah Ok thanks for your answer

But how can we do this without awk? only grep is possible and REGEX?

Du you have any idea?

Thanks for your reply,

chrism01 · 03-06-2013, 01:00 AM

Code:

 ifconfig | grep -E -o '([[:alnum:]]+:){5}[[:alnum:]]+'
E0:CB:4E:B9:5F:1A
E0:CB:4E:B9:5F:1A
52:54:00:52:23:F5

See http://linux.die.net/man/1/grep
NB: using '-a' on Linux includes installed but not active NICs.

druuna · 03-06-2013, 01:04 AM

Chris beaten me to it.

Here's one that has a regexp that's is a bit more restrictive:

Code:

ifconfig | grep -oiE '([0-9A-F]{2}:){5}[0-9A-F]{2}'
20:cf:30:39:bb:20
20:cf:30:39:bb:1f
42:3c:05:1a:38:e8
c6:d9:ab:a1:f8:38
86:26:78:65:33:73

chrism01 · 03-06-2013, 01:17 AM

Hi drunna; here's a challenge.

According to the man pages, ifconfig is deprecated and we should use the ip cmd http://linux.die.net/man/8/ip.
I'm struggling to find a soln to the OP's qn using only(!) ip & grep; keep getting the broadcast address in the results as well.
Can you do it?

druuna · 03-06-2013, 01:26 AM

Quote:

Originally Posted by chrism01

Hi drunna; here's a challenge.

According to the man pages, ifconfig is deprecated and we should use the ip cmd http://linux.die.net/man/8/ip.
I'm struggling to find a soln to the OP's qn using only(!) ip & grep; keep getting the broadcast address in the results as well.
Can you do it?

How about this;

Code:

ip link list | grep -oiE '([0-9A-F]{2}:){5}[0-9A-F]{2} '
00:00:00:00:00:00 
20:cf:30:39:bb:20 
20:cf:30:39:bb:1f 
42:3c:05:1a:38:e8 
86:26:78:65:33:73 
c6:d9:ab:a1:f8:38

I have to be honest: I did cheat (there's an extra space after the HWaddr......)

chrism01 · 03-06-2013, 01:28 AM

You sneaky devil

I'm definitely giving you Rep pts for that

grail · 03-06-2013, 08:27 AM

How about:

Code:

ip l | grep -oiP '(\w{2}:?){6}(?= )'

No pesky space

David the H. · 03-09-2013, 07:56 AM

There's a regex character class expressly defined for hexdecimal, BTW: "[:xdigit:]". It's equivalent to "[0-9a-fA-F]".

PS: chrism01's solution in post #2 can be simplified to use awk only.

Code:

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