How can I shuffle the lines of a text file on the Unix command line or in a shell script

Question

I want to shuffle the lines of a text file randomly and create a new file  The file may have several thousands of lines   How can I do that with cat  awk  cut  etc

User · Answer

We have a package to do the very job     sudo apt-get install randomize-lines   Example   Create an ordered list of numbers  and save it to 1000 txt     seq 1000  gt  1000 txt   to shuffle it  simply use    rl 1000 txt

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Here is a first try that s easy on the coder but hard on the CPU which prepends a random number to each line  sorts them and then strips the random number from each line  In effect  the lines are sorted randomly   cat myfile   awk  BEGIN srand     print rand    t  0     sort -k1 -n   cut -f2-  gt  myfile shuffled

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I use a tiny perl script  which I call  unsort       usr bin perl use List  Util  shuffle    list    lt STDIN gt   print shuffle  list     I ve also got a NULL-delimited version  called  unsort0      handy for use with find -print0 and so on   PS   Voted up  shuf  too  I had no idea that was there in coreutils these days     the above may still be useful if your systems doesn t have  shuf

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In windows You may try this batch file to help you to shuffle your data txt  The usage of the batch code is  C   gt  type list txt   shuffle bat  gt  maclist temp txt   After issuing this command  maclist temp txt will contain a randomized list of lines   Hope this helps

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Perl one-liner would be a simple version of Maxim s solution  perl -MList  Util shuffle -e  print shuffle  lt STDIN gt      lt  myfile

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Ruby FTW   ls   ruby -e  puts STDIN readlines shuffle

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If you have Scala installed  here s a one-liner to shuffle the input   ls -1   scala -e  for  l  lt - util Random shuffle io Source stdin getLines toList   println l

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Not mentioned as of yet    The unsort util   Syntax  somewhat playlist oriented    unsort  -hvrpncmMsz0l   --help   --version   --random   --heuristic          --identity   --filenames  profile    --separator sep   --concatenate           --merge   --merge-random   --seed integer   --zero-terminated   --null           --linefeed   file       msort can shuffle by line  but it s usually overkill   seq 10   msort -jq -b -l -n 1 -c r

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here s an awk script  awk  BEGIN srand       lines   d   0   END      while  1       if  e  d   break          RANDOM   int 1   rand     d          if   RANDOM in lines                 print lines RANDOM              delete lines RANDOM                e                    file   output    cat file 1 2 3 4 5 6 7 8 9 10      shell sh 7 5 10 9 6 8 2 1 3 4

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One liner for Python based on scai s answer  but a  takes stdin  b  makes the result repeatable with seed  c  picks out only 200 of all lines     cat file   python -c  import random  sys     random seed 100   print    join random sample sys stdin readlines    200          gt  200lines txt

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This answer complements the many great existing answers in the following ways    The existing answers are packaged into flexible shell functions    The functions take not only stdin input  but alternatively also filename arguments The functions take extra steps to handle SIGPIPE in the usual way  quiet termination with exit code 141   as opposed to breaking noisily  This is important when piping the function output to a pipe that is closed early  such as when piping to head   A performance comparison is made       POSIX-compliant function based on awk  sort  and cut  adapted from the OP s own answer    shuf     awk  BEGIN  srand    OFMT    17f    print rand     0                         sort -k1 1n   cut -d     -f2-       Perl-based function - adapted from Moonyoung Kang s answer    shuf     perl -MList  Util shuffle -e  print shuffle  lt  gt                Python-based function  adapted from scai s answer    shuf     python -c   import sys  random  fileinput  from signal import signal  SIGPIPE  SIG DFL      signal SIGPIPE  SIG DFL   lines  line for line in fileinput input        random shuffle lines   sys stdout write    join lines               See the bottom section for a Windows version of this function    Ruby-based function  adapted from hoffmanc s answer    shuf     ruby -e  Signal trap  SIGPIPE    SYSTEM DEFAULT                         puts ARGF readlines shuffle              Performance comparison   Note  These numbers were obtained on a late-2012 iMac with 3 2 GHz Intel Core i5 and a Fusion Drive  running OSX 10 10 3  While timings will vary with OS used  machine specs  awk implementation used  e g   the BSD awk version used on OSX is usually slower than GNU awk and especially mawk   this should provide a general sense of relative performance   Input file is a 1-million-lines file produced with seq -f  line   0f  1000000  Times are listed in ascending order  fastest first     shuf   0 090s  Ruby 2 0 0   0 289s  Perl 5 18 2   0 589s  Python   1 342s with Python 2 7 6  2 407s    with Python 3 4 2  awk   sort   cut   3 003s with BSD awk  2 388s with GNU awk  4 1 1   1 811s with mawk  1 3 4       For further comparison  the solutions not packaged as functions above    sort -R  not a true shuffle if there are duplicate input lines    10 661s - allocating more memory doesn t seem to make a difference  Scala   24 229s  bash loops   sort   32 593s    Conclusions    Use shuf  if you can - it s the fastest by far  Ruby does well  followed by Perl  Python is noticeably slower than Ruby and Perl  and  comparing Python versions  2 7 6 is quite a bit faster than 3 4 1 Use the POSIX-compliant awk   sort   cut combo as a last resort  which awk implementation you use matters  mawk is faster than GNU awk  BSD awk is slowest   Stay away from sort -R  bash loops  and Scala      Windows versions of the Python solution  the Python code is identical  except for variations in quoting and the removal of the signal-related statements  which aren t supported on Windows     For PowerShell  in Windows PowerShell  you ll have to adjust  OutputEncoding if you want to send non-ASCII characters via the pipeline       Call as  shuf someFile txt  or  Get-Content someFile txt   shuf  function shuf      Input   python -c    import sys  random  fileinput  lines  line for line in fileinput input     random shuffle lines   sys stdout write    join lines       args       Note that PowerShell can natively shuffle via its Get-Random cmdlet  though performance may be a problem   e g   Get-Content someFile txt   Get-Random -Count   int   MaxValue    For cmd exe  a batch file     Save to file shuf cmd  for instance    echo off python -c  import sys  random  fileinput  lines  line for line in fileinput input     random shuffle lines   sys stdout write    join lines

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If like me you came here to look for an alternate to shuf for macOS then use randomize-lines   Install randomize-lines homebrew  package  which has an rl command which has similar functionality to shuf   brew install randomize-lines  Usage  rl  OPTION      FILE     Randomize the lines of a file  or stdin      -c  --count N  select N lines from the file   -r  --reselect lines may be selected multiple times   -o  --output FILE                  send output to file   -d  --delimiter DELIM                  specify line delimiter  one character    -0  --null     set line delimiter to null character                   useful with find -print0    -n  --line-number                  print line number with output lines   -q  --quiet  --silent                  do not output any errors or warnings   -h  --help     display this help and exit   -V  --version  output version information and exit

User · Answer

Simple awk-based function will do the job   shuffle          awk  BEGIN srand      printf   06d  s n   rand   1000000   0      sort -n   cut -c8-     usage   any command   shuffle   This should work on almost any UNIX  Tested on Linux  Solaris and HP-UX   Update   Note  that leading zeros   06d  and rand   multiplication makes it to work properly also on systems where sort does not understand numbers  It can be sorted via lexicographical order  a k a  normal string compare

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A simple and intuitive way would be to use shuf   Example   Assume words txt as   the an linux ubuntu life good breeze   To shuffle the lines  do     shuf words txt   which would throws the shuffled lines to standard output  So  you ve to pipe it to an output file like     shuf words txt  gt  shuffled words txt   One such shuffle run could yield   breeze the linux an ubuntu good life

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This is a python script that I saved as rand py in my home folder      bin python  import sys import random  if   name         main       with open sys argv 1    r   as f      flist   f readlines       random shuffle flist       for line in flist        print line strip     On Mac OSX sort -R and shuf are not available so you can alias this in your bash profile as   alias shuf  python rand py

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A one-liner for python   python -c  import random  sys  lines   open sys argv 1   readlines    random shuffle lines   print    join lines    myFile   And for printing just a single random line   python -c  import random  sys  print random choice open sys argv 1   readlines      myFile   But see this post for the drawbacks of python s random shuffle    It won t work well with many  more than 2080  elements

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Another awk variant      usr bin awk -f   usage    awk -f randomize lines awk lines txt   usage after  chmod  x randomize lines awk     randomize lines awk lines txt  BEGIN     FS     n     srand           lines  rand       0     END     for  k in lines        print lines k

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You can use shuf  On some systems at least  doesn t appear to be in POSIX    As jleedev pointed out  sort -R might also be an option  On some systems at least  well  you get the picture  It has been pointed out that sort -R doesn t really shuffle but instead sort items according to their hash value    Editor s note  sort -R almost shuffles  except that duplicate lines   sort keys always end up next to each other  In other words  only with unique input lines   keys is it a true shuffle  While it s true that the output order is determined by hash values  the randomness comes from choosing a random hash function - see manual

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This bash function has the minimal dependency only sort and bash    shuf     while read -r x do     echo  RANDOM   x1f  x done   sort   while IFS    x1f  read -r x y do     echo  y done

[shell] How can I shuffle the lines of a text file on the Unix command line or in a shell script?

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