"How to randomly select lines from a text file"

Post #302720475 by drl on Wednesday 24th of October 2012 09:00:25 AM

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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fmt(1)							      General Commands Manual							    fmt(1)

NAME
fmt - format text SYNOPSIS
width] [file...] DESCRIPTION
The command is a simple text formatter that fills and joins lines to produce output lines of (up to) the number of characters specified in the width option. The default width is 72. concatenates the arguments. If none are given, formats text from the standard input. Blank lines are preserved in the output, as is the spacing between words. does not fill lines beginning with a period for compatibility with Nor does it fill lines starting with Indentation is preserved in the output and input lines with differing indentation are not joined (unless is used). can also be used as an in-line text filter for the command: reformats the text between the cursor location and the end of the paragraph. Options recognizes the following options: Crown margin mode. Preserve the indentation of the first two lines within a paragraph and align the left margin of each subsequent line with that of the second line. This is useful for tagged paragraphs. Split lines only. Do not join short lines to form longer ones. This prevents sample lines of code, and other such "formatted" text, from being unduly combined. Fill output lines to up to width columns. WARNINGS
The width option is acceptable for BSD compatibility, but it may go away in future releases. SEE ALSO
nroff(1), vi(1). fmt(1)

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