shuffle the lines of a large file

[Eddie Corns]

"Joerg Schuster" <joerg.schuster.REMOVETHIS at gmail.com> writes:

>Hello,

>I am looking for a method to "shuffle" the lines of a large file.

>I have a corpus of sorted and "uniqed" English sentences that has been
>produced with (1):

>(1) sort corpus | uniq > corpus.uniq

>corpus.uniq is 80G large. The fact that every sentence appears only
>once in corpus.uniq plays an important role for the processes
>I use to involve my corpus in.  Yet, the alphabetical order is an
>unwanted side effect of (1): Very often, I do not want (or rather, I
>do not have the computational capacities) to apply a program to all of
>corpus.uniq. Yet, any series of lines of corpus.uniq is obviously a
>very lopsided set of English sentences.

>So, it would be very useful to do one of the following things:

>- produce corpus.uniq in a such a way that it is not sorted in any way
>- shuffle corpus.uniq > corpus.uniq.shuffled

>Unfortunately, none of the machines that I may use has 80G RAM.
>So, using a dictionary will not help.

>Any ideas?

Instead of shuffling the file itself maybe you could index it (with dbm for
instance) and select random lines by using random indexes whenever you need a
sample.

Eddie