gistfile1.txt

Lets break the full command down
ip -o link show eth0 | awk '{ for (x=1; x<=NF;x++) if ($x=="link/ether") print $(x+1)}'

############################################################
# If we just run the ip -o link command against regular, it just adds the ip link into one line.
This is useful if you want to awk after

ip -o link show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 1000\    link/ether 00:1a:4a:16:01:86 brd ff:ff:ff:ff:ff:ff

ip link show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 1000
    link/ether 00:1a:4a:16:01:86 brd ff:ff:ff:ff:ff:ff
###############################################################

The next code is an awk, it will take all of these arguments.
awk '{ for (x=1; x<=NF;x++) if ($x=="link/ether") print $(x+1)}'

To understand this command, we first have to understand the awk NF variable
-->: http://www.thegeekstuff.com/2010/01/8-powerful-awk-built-in-variables-fs-ofs-rs-ors-nr-nf-filename-fnr/?ref=binfind.com/web
As can be seen from the solution, NF is counting the fields.

###########################################
So...lets break down for (x=1; x<=NF;x++)

for (x=1 means:
While this statement is true
Set x to the value of 1.

x=1;x<=NF
if x is less than the total, add one to x)

So until the value of x reaches NF, the statement will be true and be able to execute.
###########################################

Next part:
if ($x=="link/ether") 
If the value of x is equal to link ether field.

then
print $(x+1)}'
Which translates to print the value of variable x + 1


After which we get the Mac Address:
ip -o link show eth0 | awk '{ for (x=1; x<=NF;x++) if ($x=="link/ether") print $(x+1)}'
00:1a:4a:16:01:86