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Full Discussion: Get 20% of lines in File randomly
Top Forums Shell Programming and Scripting Get 20% of lines in File randomly Post 302707225 by Lem on Friday 28th of September 2012 07:39:08 AM
Old 09-28-2012
If I'm right your problem is to randomly generate N integers in the range [1;M], where M is the number of lines in the file, and N is a rounded percentage of M.

Before going on: are repetitions allowed? In other words, may a number (a line in the file) be randomly selected more than once?

And: what are your shell and OS?

EDIT: solution proposed

However, this is a possible solution working on linux/bash, with repetitions not allowed:
Code:
#!/bin/bash
range=$(wc -l "$1" | cut -d " " -f1)
(( $range > 32768 )) && exit              ### max number of lines for this script: 32768
percent=$2                                ### set this  as you like, [1-100]
(( 0 < $2 )) && (( $2 < 101 )) || exit
lim=$(( $range * $percent / 100 ))
for ((i=0;i<lim;i++)); do
        num=$(( $RANDOM % $range + 1 ));
        arr[$i]=$num;
        for ((j=0;j<i;j++)); do
                (( ${arr[$j]} == $num )) && {
                        let i--
                        break; }
        done
done

for linenum in "${arr[@]}"; do
        line=$(sed -n "$linenum p" "$1")
        ### your stuff here, for example: ###
        echo "$linenum"$'\t'"### $line"
done

exit 0

Usage:
Code:
lem@biggy:/tmp$ ./file2 file2 30
6	### lim=$(( $range * $percent / 100 ))
19	###         ### your stuff here, for example: ###
11	###                 (( ${arr[$j]} == $num )) && {
10	###         for ((j=0;j<i;j++)); do
5	### (( 0 < $2 )) && (( $2 < 101 )) || exit
4	### percent=$2                                ### set this  as you like, [1-100]

--
Bye
Last edited by Lem; 09-28-2012 at 11:36 AM.. Reason: Solution proposed
This User Gave Thanks to Lem For This Post:
chercheur857
 

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LEARN ABOUT DEBIAN

ppmtosixel

ppmtosixel(1)						      General Commands Manual						     ppmtosixel(1)

NAME

       ppmtosixel - convert a portable pixmap into DEC sixel format

SYNOPSIS

       ppmtosixel [-raw] [-margin] [ppmfile]

DESCRIPTION

       Reads  a  portable  pixmap  as input.  Produces sixel commands (SIX) as output.	The output is formatted for color printing, e.g. for a DEC
       LJ250 color inkjet printer.

       If RGB values from the PPM file do not have maxval=100, the RGB values are rescaled.  A printer control header and a color assignment table
       begin the SIX file.  Image data is written in a compressed format by default.  A printer control footer ends the image file.

OPTIONS

       -raw   If  specified,  each  pixel  will  be explicitly described in the image file.  If -raw is not specified, output will default to com-
	      pressed format in which identical adjacent pixels are replaced by "repeat pixel" commands.  A raw file is often an order	of  magni-
	      tude larger than a compressed file and prints much slower.

       -margin
	      If  -margin  is not specified, the image will be start at the left margin (of the window, paper, or whatever).  If -margin is speci-
	      fied, a 1.5 inch left margin will offset the image.

PRINTING

       Generally, sixel files must reach the printer unfiltered.  Use the lpr -x option or cat filename > /dev/tty0?.

BUGS

       Upon rescaling, truncation of the least significant bits of RGB values may result in poor color conversion.  If the original PPM maxval was
       greater	than  100,  rescaling  also reduces the image depth.  While the actual RGB values from the ppm file are more or less retained, the
       color palette of the LJ250 may not match the colors on your screen.  This seems to be a printer limitation.

SEE ALSO

       ppm(5)

AUTHOR

       Copyright (C) 1991 by Rick Vinci.

								   26 April 1991						     ppmtosixel(1)
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