Re^3: Sorting a text file

You are quite right. However if you have duplicate keys how do you expect the sort to arrange those lines? Do you fall back to a secondary key, or does it not matter, or do you retain the original file order? You could for example rely on sort's stability in recent versions of Perl to retain the lines with identical keys in file order:

use strict;
use warnings;

print sort {substr ($a, 9, 4) cmp substr ($b, 9, 4)} <DATA>

__DATA__
...
[download]

Prints (using the original data):

77809    7211    CA84985    54E
77875    7725    CA84985    54E
77822    7874    CA84985    54E
77873    8003    CA84985    54E
77826    8040    CA84985    54E
77873    8123    CA84985    54E
77819    8503    CA84985    54E
77872    8511    CA84985    54E
77876    8543    CA84985    54E
77884    8543    CA84985    54E
77822    9908    CA84985    54E
[download]

DWIM is Perl's answer to Gödel

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Re^4: Sorting a text file by ArifS (Beadle) on Dec 06, 2016 at 17:57 UTC
This seems to work with digits as shows above, however, I couldn't make it work for the following while sorting with the 2nd word (combination)- `_DATA_ CCCCCC-NF-33 LONDON_JAM_2AAA END-ONE_2TWO DDDDDD-NF_52 VENICE_CCC_1ZZZ WHAT_WHEN-1WHY KKKKK-INF_44 JAMAICA_AAA_3TTT HOW-WHERE_3WHAT AAAAA-INF-32 LONDON_JAM_2AAA END-ONE_2TWO BBBBB-INF-12 JAMAICA_AAA_3TTT WHAT_WHEN-1WHY VVVVV-INF_24 VENICE_CCC_1ZZZ END-ONE_2TWO` [download] Any suggestion?	[reply] [d/l]
Re^5: Sorting a text file by tybalt89 (Monsignor) on Dec 06, 2016 at 18:11 UTC
Suggestion: then sort by the second word `#!/usr/bin/perl # http://perlmonks.org/?node_id=1177316 use strict; use warnings; print sort { (split ' ', $a)[1] cmp (split ' ', $b)[1] } <DATA>; __DATA__ CCCCCC-NF-33 LONDON_JAM_2AAA END-ONE_2TWO DDDDDD-NF_52 VENICE_CCC_1ZZZ WHAT_WHEN-1WHY KKKKK-INF_44 JAMAICA_AAA_3TTT HOW-WHERE_3WHAT AAAAA-INF-32 LONDON_JAM_2AAA END-ONE_2TWO BBBBB-INF-12 JAMAICA_AAA_3TTT WHAT_WHEN-1WHY VVVVV-INF_24 VENICE_CCC_1ZZZ END-ONE_2TWO` [download]	[reply] [d/l]
Re^6: Sorting a text file by ArifS (Beadle) on Dec 06, 2016 at 18:25 UTC
This is a good solution. Thanks	[reply]