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Full Discussion: How to randomly select lines from a text file
Top Forums UNIX for Dummies Questions & Answers How to randomly select lines from a text file Post 302720825 by Scrutinizer on Wednesday 24th of October 2012 04:49:58 PM
Old 10-24-2012
In the order of lines in the file, without all lines in memory:
Code:
awk '
  NR==FNR { next }
  FNR==1{
    srand;
    n=NR-1
    for(i=1; i<=200; i++) {
      line=0
      while(!line || line in A) line=int(rand*n)+1
      A[line]
    }
  } 
  FNR in A
' infile infile


In the order of the selection, with all lines in the file in memory..
Code:
awk '
  { R[NR]=$0 }
  END{
    srand;
    n=NR
    for(i=1; i<=200; i++) {
      line=0
      while(!line || line in A) line=int(rand*n)+1
      A[line]
      print R[line]
    }
  } 
' infile

 

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LEARN ABOUT SUSE

prunehistory

PRUNEHISTORY(8) 					    InterNetNews Documentation						   PRUNEHISTORY(8)

NAME

       prunehistory - Remove tokens from Usenet history file

SYNOPSIS

       prunehistory [-p] [-f filename]

DESCRIPTION

       prunehistory modifies a history(5)-format text file to "remove" a set of tokens from it.  The tokens are removed by overwriting them with
       spaces, so that the size and position of any following entries does not change.	This has an effect similar to expiring the article, in
       that it is still mentioned in the history database but cannot be retrieved.

       prunehistory reads the standard input.  The input is taken as a set of lines.  Blank lines and lines starting with a number sign ("#") are
       ignored.  All other lines should consist of a message-ID followed by zero or more other fields (which are ignored).  The message-ID is used
       as the dbz(3) key to get an offset into the text file.  Since innd only appends to the text file, prunehistory does not need to have any
       interaction with it.

OPTIONS

       -p  prunehistory will normally complain about lines that do not follow the correct format.  If the -p flag is used, then the program will
	   silently print any invalid lines on its standard output.  (Blank lines and comment lines are also passed through.)

	   This can be useful when prunehistory is used as a filter for other programs such as reap (a legacy program, probably no longer useful
	   with current versions of INN, but still available at <ftp://ftp.ruhr-uni-bochum.de/.subdisc1/local/jk.collection/>).

       -f filename
	   The default name of the history file is pathdb/history; to specify a different name, use the -f flag.

HISTORY

       Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews.  Converted to POD by Julien Elie.

       $Id: prunehistory.pod 8592 2009-08-20 23:46:25Z eagle $

SEE ALSO

       dbz(3), history(5), innd(8).

INN 2.5.2							    2009-09-11							   PRUNEHISTORY(8)
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