[SOLVED] sed to insert colon in a mac address

Issue

I have a list of mac addresses in this format:

412010000018
412010000026
412010000034

I want this output:

41:20:10:00:00:18
41:20:10:00:00:26
41:20:10:00:00:34

I tried this, but did not work:

sed 's/([0-9]{2})([0-9]{2})([0-9]{2})([0-9]{2})/\1:\2:\3:\4/g' mac_list

How should I do it?

Solution

You have to use the correct sed syntax:

\{I\}
     matches exactly I sequences (I is a decimal integer;
     for portability, keep it between 0 and 255 inclusive).

\(REGEXP\)
     Groups the inner REGEXP as a whole, this is used for back references.

Here is an example command that covers the first 2 fields

     sed 's/^\([0-9A-Fa-f]\{2\}\)\([0-9A-Fa-f]\{2\}\).*$/\1:\2:/'

The following command can process a complete MAC address and is easy to read:

 sed -e 's/^\([0-9A-Fa-f]\{2\}\)/\1_/'  \
     -e 's/_\([0-9A-Fa-f]\{2\}\)/:\1_/' \
     -e 's/_\([0-9A-Fa-f]\{2\}\)/:\1_/' \
     -e 's/_\([0-9A-Fa-f]\{2\}\)/:\1_/' \
     -e 's/_\([0-9A-Fa-f]\{2\}\)/:\1_/' \
     -e 's/_\([0-9A-Fa-f]\{2\}\)/:\1/'

Following the idea from a perl solution posted here by @Qtax with global substitutions one can get a shorter solution:

 sed -e 's/\([0-9A-Fa-f]\{2\}\)/\1:/g' -e 's/\(.*\):$/\1/'

Answered By - Dima Chubarov

Answer Checked By - Dawn Plyler (WPSolving Volunteer)