How to sort IP addresses using the GNU sort utility.
Here’s the invocation that works. It’s explained in the long answer that follows.
sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4
More than once I’ve been confronted with a list of IP addresses that I’ve wanted to sort into numeric order. Trouble is, the dotted-quad notation isn’t sort-friendly. Consider the following raw list of addresses.
$ cat addresses.txt 188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199
sort will rely on alphabetic order, which certainly
won’t do what you want:
$ sort addresses.txt 188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199
There are so many mistakes in this ordering I’m not even going to try to list them all.
The situation is only marginally improved when using the
$ sort -n addresses.txt 188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199
The first set of numbers in each dotted-quad sort correctly—5 preceeds 19, and 129 is at the tail end—but the internal numbering still gets improper treatment. 188.8.131.52 is listed prior to 184.108.40.206 because 220 is alphabetically prior to 24. Likewise the two 19.20.x.x addresses are mixed up because 203 is alphabetically prior to 21.
The solution is to tell
sort to order the list numerically,
considering each address as a set of four numeric fields, each separated
by a dot.
$ sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4 addresses.txt 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199 188.8.131.52 184.108.40.206
In English, you’re saying, Yo,
sort! I’ve got here a list of numbers
-n), but each item in the list consists of some subnumbers, fields
set apart from the others by a dot (
-t .). Sort first by the first
field, and only the first field (
-k 1,1), then by the second and only
the second (
-k 2,2), and so on (
-k 3,3 -k 4,4).