sort -R or shuf ?

ychaouche · 12-31-2020, 06:52 AM

Dear LQ,

What is your preferred way of sorting randomly, sort -R or shuf ?

pan64 · 12-31-2020, 06:59 AM

sort -R works differently, read man page about that. So use what you really need.

ychaouche · 12-31-2020, 07:21 AM

sort by random hash of key... I don't even know what's
that supposed to mean ? I never thought of a hash as
possibly being random, I thought they were
deterministic.

ondoho · 12-31-2020, 07:26 AM

Quote:

Originally Posted by ychaouche

sort by random hash of key...

Where are you getting this? Both my systems' 'sort' man pages say this:

Code:

  -R, --random-sort
          shuffle, but group identical keys.

That is obviously different from just "shuffle".

ychaouche · 12-31-2020, 09:00 AM

Code:

ychaouche#ychaouche-PC 15:57:56 ~/DOWNLOADS/APPS/THUNDERBIRD/thunderbird $ sort --version
sort (GNU coreutils) 8.21
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Mike Haertel and Paul Eggert.
ychaouche#ychaouche-PC 15:58:57 ~/DOWNLOADS/APPS/THUNDERBIRD/thunderbird $ sort --help | grep '\-R'
  -R, --random-sort           sort by random hash of keys
                                numeric -n, random -R, version -V
ychaouche#ychaouche-PC 16:00:15 ~/DOWNLOADS/APPS/THUNDERBIRD/thunderbird $ man --pager=cat sort | grep '\-R' -A1
       -R, --random-sort
              sort by random hash of keys
--
              sort according to WORD: general-numeric -g, human-numeric -h, month -M, numeric -n, random -R, version -V

ychaouche#ychaouche-PC 16:00:40 ~/DOWNLOADS/APPS/THUNDERBIRD/thunderbird $

shruggy · 12-31-2020, 09:12 AM

Sadly, the definitive documentation for GNU tools are not man pages, but info manuals. For sort -R, it says:

Quote:

-R
--random-sort
--sort=random

Sort by hashing the input keys and then sorting the hash values. Choose the hash function at random, ensuring that it is free of collisions so that differing keys have differing hash values. This is like a random permutation of the inputs (see shuf invocation), except that keys with the same value sort together.

If multiple random sort fields are specified, the same random hash function is used for all fields. To use different random hash functions for different fields, you can invoke sort more than once.

The choice of hash function is affected by the --random-source option.

pan64 · 12-31-2020, 12:23 PM

That is more or less identical, but you are right, this info manual is better - although sort by those hashes means really grouping by identical keys.
And also means this is reproducible, so the sort will give always the same "random" result with the same hashing algorithm (see --random-source=FILE).

It is still different from the real shuffle.

ychaouche · 01-03-2021, 04:33 AM

So shuffle is more random ?