How to randomly select lines from a text file Post: 302720475

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Top Forums UNIX for Dummies Questions & Answers How to randomly select lines from a text file Post 302720475 by drl on Wednesday 24th of October 2012 09:00:25 AM

10-24-2012

Registered User

Hi.

There are a number of commonly-available utilities to do this. Here is a demonstration of two:

Code:

#!/usr/bin/env bash

# @(#) s1	Demonstrate random selection of lines with rl, shuf.

pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
C=$HOME/bin/context && [ -f $C ] && $C rl shuf

pl " Lines selected from:"
cat data0

# Prepare data file from single line of words.
tr ' ' '\n' < data0 > data1

pl " Results from shuf, 1:"
shuf -n 3 data1

pl " Results from shuf, 2:"
shuf -n 3 data1

pl " Results from rl, 1:"
rl -c 3 data1

pl " Results from rl, 2:"
rl -c 3 data1

exit 0

producing:

Code:

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0.8 (lenny) 
bash GNU bash 3.2.39
rl 0.2.7
shuf (GNU coreutils) 6.10

-----
 Lines selected from:
foo bar baz qux quux corge grault garble warg fred plugh xyzzy thud

-----
 Results from shuf, 1:
quux
thud
qux

-----
 Results from shuf, 2:
thud
xyzzy
quux

-----
 Results from rl, 1:
corge
qux
grault

-----
 Results from rl, 2:
thud
corge
warg

You may need to install these from your distribution repository. See man pages for details.

See also Algorithm::Numerical::Sample - search.cpan.org if a perl module is desirable.

Best wishes ... cheers, drl

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LEARN ABOUT REDHAT

prunehistory

PRUNEHISTORY(8) 					      System Manager's Manual						   PRUNEHISTORY(8)

NAME

       prunehistory - remove file names from Usenet history file

SYNOPSIS

       prunehistory [ -f filename ] [ -p ]

DESCRIPTION

       Prunehistory  modifies  the  history(5)	text file to ``remove'' a set of filenames from it.  The filenames are removed by overwriting them
       with spaces, so that the size and position of any following entries does not change.

       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 are should consist of a Message-ID followed by zero or more filenames.

       The  Message-ID	is  used as the dbz(3) key to get an offset into the text file.  If no filenames are mentioned on the input line, then all
       filenames in the text are ``removed.''  If any filenames are mentioned, they are converted into the history file notation.  If they  appear
       in the line for the specified Message-ID then they are removed.

       Since innd(8) 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.

       -f     The default name of the history file is <pathdb in inn.conf>/history; to specify a different name, use the ``-f'' flag.

HISTORY

       Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews.  This is revision 1.7, dated 1998/04/09.

SEE ALSO

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

																   PRUNEHISTORY(8)

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