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
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
This User Gave Thanks to drl For This Post:
 
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fmt(1)								   User Commands							    fmt(1)

NAME
fmt - simple text formatters SYNOPSIS
fmt [-cs] [-w width | -width] [inputfile]... DESCRIPTION
fmt is a simple text formatter that fills and joins lines to produce output lines of (up to) the number of characters specified in the -w width option. The default width is 72. fmt concatenates the inputfiles listed as arguments. If none are given, fmt formats text from the standard input. Blank lines are preserved in the output, as is the spacing between words. fmt does not fill nor split lines beginning with a `.' (dot), for compatibility with nroff(1). Nor does it fill or split a set of contiguous non-blank lines which is determined to be a mail header, the first line of which must begin with "From". Indentation is preserved in the output, and input lines with differing indentation are not joined (unless -c is used). fmt can also be used as an in-line text filter for vi(1). The vi command: !}fmt reformats the text between the cursor location and the end of the paragraph. OPTIONS
-c 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. -s Split lines only. Do not join short lines to form longer ones. This prevents sample lines of code, and other such for- matted text, from being unduly combined. -w width | -width Fill output lines to up to width columns. OPERANDS
inputfile Input file. ENVIRONMENT VARIABLES
See environ(5) for a description of the LC_CTYPE environment variable that affects the execution of fmt. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ SEE ALSO
nroff(1), vi(1), attributes(5), environ(5) NOTES
The -width option is acceptable for BSD compatibility, but it may go away in future releases. SunOS 5.11 9 May 1997 fmt(1)

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