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Full Discussion: how to choose random columns
Top Forums Shell Programming and Scripting how to choose random columns Post 302516668 by drl on Sunday 24th of April 2011 06:22:00 PM
Old 04-24-2011
Hi.

With standard utilities:
Code:
#!/usr/bin/env bash

# @(#) s1	Demonstrate extraction of random number of columns.

# Utility functions: print-as-echo, print-line-with-visual-space, debug.
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 seq rl tr sed cut

N=${1-3}
FILE=data1

# Generate N numbers in random sequence, range 1 - number-of-columns
cols=$( seq 1 10 | rl -c $N | tr '\n' ',' | sed 's/.$//' )

pl " Random columns: $cols"

cut -d" " -f"$cols" $FILE

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 5.0.7 (lenny) 
GNU bash 3.2.39
seq (GNU coreutils) 6.10
rl 0.2.7
tr (GNU coreutils) 6.10
GNU sed version 4.1.5
cut (GNU coreutils) 6.10

-----
 Random columns: 7,9,2
1,2 1,7 1,9
2,2 2,7 2,9
3,2 3,7 3,9
4,2 4,7 4,9

and choosing a different N:
Code:
% ./s1 5

... omitted

-----
 Random columns: 8,2,9,1,5
1,1 1,2 1,5 1,8 1,9
2,1 2,2 2,5 2,8 2,9
3,1 3,2 3,5 3,8 3,9
4,1 4,2 4,5 4,8 4,9

Best wishes ... cheers, drl
This User Gave Thanks to drl For This Post:
mira
 

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LEARN ABOUT REDHAT

seq

SEQ(1)									FSF								    SEQ(1)

NAME

       seq - print a sequence of numbers

SYNOPSIS

       seq [OPTION]... LAST
       seq [OPTION]... FIRST LAST
       seq [OPTION]... FIRST INCREMENT LAST

DESCRIPTION

       Print numbers from FIRST to LAST, in steps of INCREMENT.

       -f, --format=FORMAT
	      use printf style floating-point FORMAT (default: %g)

       -s, --separator=STRING
	      use STRING to separate numbers (default: 
)

       -w, --equal-width
	      equalize width by padding with leading zeroes

       --help display this help and exit

       --version
	      output version information and exit

       If FIRST or INCREMENT is omitted, it defaults to 1.  FIRST, INCREMENT, and LAST are interpreted as floating point values.  INCREMENT should
       be positive if FIRST is smaller than LAST, and negative otherwise.  When given, the FORMAT argument must contain exactly one of the printf-
       style, floating point output formats %e, %f, %g

AUTHOR

       Written by Ulrich Drepper.

REPORTING BUGS

       Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT

       Copyright (C) 2002 Free Software Foundation, Inc.
       This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
       LAR PURPOSE.

SEE ALSO

       The full documentation for seq is maintained as a Texinfo manual.  If the info and seq programs are properly installed at  your	site,  the
       command

	      info seq

       should give you access to the complete manual.

seq (coreutils) 4.5.3						   February 2003							    SEQ(1)
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