Sorting IP addresses in vim - sorting

Question

I have just discovered the command :sort n in vim (how did I not know about that?!), which has almost done exactly what I need.
What I am trying to sort, though, is a long list of IP addresses (it's an "allow hosts" file to be Included into our apache config), and it would be nice for :sort n to be able to recognise that 123.45.6.7 should sort before 123.45.16.7 (for example).
Is it a safe assumption that I should be less OCD about it and not worry, because I'm not going to be able to do this without a mildly-complex sed or awk command or something?
To be clear, the rows all look something like:
Allow from 1.2.3.4
Allow from 5.6.7.8
Allow from 9.10.11.12
etc

Answer 1

Vim sort seems to be stable in practice (but it is not guaranteed). Therefore you can try:
:%sort n /.*\./
:%sort n /\.\d\+\./
:%sort n /\./
:%sort n
Which will sort by number after the last dot (* is greedy), then by number after the first dot following a dot and digits, then by number after the first dot, and last by the first number.

Answer 2

A straightforward way to achieve the correct sorting order without
relying on the stability of the sorting algorithm implemented by the
:sort command, is to prepend zeroes to the numbers within the IP
addresses, so that all of the components in them consist of exactly
three digits.
Prepend zeros to the single-digit and two-digit numbers:
:%s/\<\d\d\?\>/0&/g|%&&
Sort the lines comparing IP addresses as text:
:sort r/\(\d\{3}\)\%(\.\d\{3}\)\{3}/
Strip redundant leading zeros:
:%s/\<00\?\ze\d//g
To run all three steps as a single command, one can use the following
one-liner:
:%s/\<\d\d\?\>/0&/g|%&&|sor r/\(\d\{3}\)\%(\.\d\{3}\)\{3}/|%s/\<00\?\ze\d//g

Answer 3

I'm not a vim user so I can't offer a direct way to do it with builtin commands, however it's possible to replace a section of text with the output of it run through a command. So, a simple script like this could be used:
#!/usr/bin/python
import sys
input_lines = sys.stdin.readlines()
sorted_lines = sorted(input_lines,
key=lambda line: map(int, line.split()[-1].split('.')))
for line in sorted_lines:
sys.stdout.write(line)
See https://www.linux.com/learn/tutorials/442419-vim-tips-working-with-external-commands, section "Filtering text through external filters", which explains how you can use this as a filter within vim.
This script should do what you want and will work on any region where all the selected lines end in an IPv4 address.

Answer 4

You can use:
:%!sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n
-t . means use . as delimiter.
Then sort numerically from 4th column to 1st column.