Actually, your specification has never been clear. First, you wanted 2 3 line output files from a 10 line input file with no duplicates in either of the output files. Then you wanted a single 5000 line file from a 15000 line file. Then you wanted 3 5000 line output files from a 15000 line input file. And, now you want 5 5000 line output files from a 15000 input line file. How do you randomly select 25000 lines from a 15000 line file without replacements?

If you mean that you want 5 5000 files each of which has lines from a 15000 line file with no replacements in any one of the 5 output files, why doesn't:

Code:

shuf < 15000LineFile | head -n 5000 > 5000LineFile

give you what you want (or to get 5 output files):

Code:

for i in 1 2 3 4 5
do	shuf < 15000LineFile | head -n 5000 > 5000LineFile$i
done

And, of course, Corona688's suggestion would have given you 3 5000 line files with no duplicates from your 15000 line file and a second run would give you 3 more 5000 line files to choose from...

But, of course, all of these assume that there are no duplicated lines in 15000LineFile (or if there are duplicates, you don't mind them being duplicated in one of your output files as long as there aren't more than N duplicates in an output file if there are N duplicates in your input file). Is there a chance for duplicated lines in your input file? If so, do those duplicates have to be removed before creating output files?

If we had a clearer specification of how lines in one of the output files are related to lines in other output files and whether or not there could be duplicated lines in the input file (and, if so, how they are to be handled), all of the output files could be created by a single invocation of awk.

Knowing what operating system and shell you're using would also help for several possible script suggestions.