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Full Discussion: How to select lines randomly without replacement in UNIX?
Top Forums Shell Programming and Scripting How to select lines randomly without replacement in UNIX? Post 302981473 by RavinderSingh13 on Tuesday 13th of September 2016 02:31:16 PM
Old 09-13-2016
Quote:
Originally Posted by sajmar
Thank you Corona688 for your suggestion. I only present the small example. In my case, I want to randomly choose 5000 lines out of 15000 lines. what should I do for this situation?
Hello sajmar,

Could you please try following and let me know if this helps you.
1st solution:
Code:
cat script.ksh
lines_in_file=`cat Input_file | wc -l`
file=Input_file
for val in `seq 1 5000`;  do line=$(($RANDOM*${lines_in_file}/32767+1)); sed "${line}q;d" $file >> "output"; done

OR

cat script.ksh
lines_in_file=`cat Input_file | wc -l`
file=Input_file
for val in `seq 1 5000`
do
	line=$(($RANDOM*${lines_in_file}/32767+1))
	sed "${line}q;d" $file >> "output"
done

2nd solution:
Code:
cat script.ksh
lines_in_file=`cat Input_file | wc -l`
file=Input_file
for val in `seq 1 5001`;  do line=$(($RANDOM*${lines_in_file}/32767+1)); awk -vline="$line" 'FNR==line' $file >> "output"; done

OR

cat script.ksh
lines_in_file=`cat Input_file | wc -l`
file=Input_file
for val in `seq 1 5000`
do
        line=$(($RANDOM*${lines_in_file}/32767+1))
        awk -vline="$line" 'FNR==line' $file >> "output"
done

Where $RANDOMis responsible for generating the random numbers from 0to32767.
EDIT: Above 2 solutions will give lines duplicate, then following may help you in same too.
Code:
awk 'FNR==NR {A[$1]; next} {if (FNR in A) print}' <(shuf -i 1-15000 -n5000) Input_file > output

Thanks,
R. Singh
Last edited by RavinderSingh13; 09-13-2016 at 03:39 PM.. Reason: Added one more solution succesfully for same now.
This User Gave Thanks to RavinderSingh13 For This Post:
sajmar
 

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