Shuffling lines of a file with a fixed seed?

Question

I want to shuffle the lines of a file with a fixed seed so that I always get the same random order. The command I am using is as follows:

sort -R file.txt | head -200 > file.sff

What change could I make it so that it sorts with a fixed random seed?

Answer 1

The GNU implementation of sort has a --random-source argument. Passing this argument with the name of a file with known contents will result in a reliable set of output.

See the Random sources documentation in the GNU coreutils manual, which contains the following sample implementation and example:

get_seeded_random()
{
  seed="$1"
  openssl enc -aes-256-ctr -pass pass:"$seed" -nosalt \
    </dev/zero 2>/dev/null
}

shuf -i1-100 --random-source=<(get_seeded_random 42)

Since GNU sort is also part of coreutils, the relevant documentation applies there as well:

sort --random-source=<(get_seeded_random 42) -R file.txt | head -200 > file.sff