Enhancement Requests: Add a seed value option to sort and shuf

[Thomas Müller]

Hi,

I would appreciate if sort (and shuf) had an option to specify a seed
value that could be set during random sort in order to always get the
same permutation of an input file.

Behavior now:

Two consecutive calls to sort -R give different results:

$ echo 'a b c' | tr ' ' '\n' | sort -R
a
b
c
$ echo 'a b c' | tr ' ' '\n' | sort -R
b
c
a

Wanted behavior:

Given the same seed value two consecutive calls to sort -R generate
the same permutation:
$ echo 'a b c' | tr ' ' '\n' | sort -R --seed-value=42
c
b
a
$ echo 'a b c' | tr ' ' '\n' | sort -R --seed-value=42
c
b
a

I acutally already created a sort version with the described behavior
using a new version of
isaac_seed called isaac_seed_value:

void
isaac_seed_value (struct isaac_state *s, uint32_t seed_value)
{
  isaac_seed_start (s);

  if (seed_value > 0) {
    ISAAC_SEED(s, seed_value);
  } else {

    { pid_t t = getpid ();   ISAAC_SEED (s, t); }
    { pid_t t = getppid ();  ISAAC_SEED (s, t); }
    { uid_t t = getuid ();   ISAAC_SEED (s, t); }
    { gid_t t = getgid ();   ISAAC_SEED (s, t); }

    {
      xtime_t t = gethrxtime ();
      ISAAC_SEED (s, t);
    }
  }

  isaac_seed_finish (s);
}

This basically uses a deterministic seed value if seed_value is
different from 0 and behaves like isaac_seed if not. Of course some
code in rand-isaac.{c,h}, randread.{c,h} and sort.c had to be changed
as well.

Please tell me if you think that this feature and the implementation
make sense. If so I would glady submit my changes to the git
repository.


Best,
Thomas