Randomize lines (opposite of | sort)

cat ~/SortedFile.txt | perl -wnl -e '@f=<>; END{ foreach $i (reverse 0 .. $#f) { $r=int rand ($i+1); @f[$i, $r]=@f[$r,$i] unless ($i==$r); } chomp @f; foreach $line (@f){ print $line; }}'
The sort utility is well used, but sometimes you want a little chaos. This will randomize the lines of a text file. BTW, on OS X there is no | sort -R option! There is also no | shuf These are only in the newer GNU core... This is also faster than the alternate of: | awk 'BEGIN { srand() } { print rand() "\t" $0 }' | sort -n | cut -f2-
Sample Output
cat ~/SortedFile.txt | perl -wnl -e '@f=<>; END{ foreach $i (reverse 0 .. $#f) { $r=int rand ($i+1); @f[$i, $r]=@f[$r,$i] unless ($i==$r); }  chomp @f; foreach $line (@f){ print $line; }}'

... randome lines from SortedFile.txt

0
By: drewk
2009-09-24 15:42:43

4 Alternatives + Submit Alt

What Others Think

That misses line 1. You can also do it with python and sed: f="sortedfile.txt";l=$(cat "$f" | wc -l);for i in $(python -c "from random import *;print sample(xrange(1,1+$l),$l)"| tr -d "[,]"); do sed -n "$i"p "$f"; done
Escher · 468 weeks and 5 days ago
How is it that the perl program misses 1 line? head and tail of the output are 100% different that input.
drewk · 468 weeks and 2 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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