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I have a text file that is couple GBs. I am trying to shuffle this text file in a pipe.

For example these are some sample lines of what I am using but it is not efficient and in fact the pipe does not seem to start until the whole file is read. Maybe I am wrong on it.

shuf HUGETEXTFILE.txt|some command

cat HUGETEXTFILE.txt|sort -R |some command

I also tried to use

split -n 1/numberofchunks HUGETEXTFILE.txt|sort -R|some command 

But the piping ends when the first chunk finishes.

I am trying to find an efficient way to pipe text file shuffling in a pipe because I do not want to write hundreds of files everytime I need a new way of shuffling, or random distribution.

thanks

  • Have you tried to use shuf --input-range=$LO-$HI? Instead of split ... you can give to shuf the range in linenumbers... – Hastur Jul 25 '14 at 22:31
  • Well I amm trying to shuffle the whole file at once if possible. This just sounds like it would shuffle a range from the input file. – yarun can Jul 25 '14 at 22:45
  • also that argument just creates bunch of random numbers,i am not sure if that is what I need. Can you be more elaborate please? – yarun can Jul 25 '14 at 22:48
  • Have you tried using shuf with the --output option, then using cat outfile.txt | some command. I know you said you didn't want to write hundreds of files, but this is only one and the name can be resued, meaning you should only have one. – Tyson Jul 25 '14 at 23:03
  • You do know, that there simply is no "efficient" way to shuffle a multi-GB textfile (i.e. one, that doesn't fit in RAM) - shuffling is an intrinsicly expensive operation. – Eugen Rieck Jul 25 '14 at 23:04
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You can try this approach:

cat bigfile.txt|
  while IFS= read -r line; do
    echo '%s\n' "$line" |shuf |sort -n| grep "sample";
  done

IFS is used to split the output into lines here.

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