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Top Forums UNIX for Dummies Questions & Answers How to randomly select lines from a text file Post 302720879 by alister on Wednesday 24th of October 2012 06:28:29 PM
Old 10-24-2012
Quote:
Originally Posted by Corona688
Code:
awk 'NR==FNR { B++; next }
(NR != FNR) && (!Z) {
        srand();
        if(Z < 200) exit(1); # Too few lines
        for(N=1; N<=200; N++)
        {
                V=sprintf("%d", (rand()*B)+1)+0;
                if(!(V in A)) { A[V]=1; N++ }
        }
        Z=1
} NR in A' inputfile inputfile

Looks like there are a couple of bugs there. The first, a typo of Z for B, always exits before selecting anything. The second, the for-loop post-increment expression, can cause the algorithm to yield anywhere between 1 and 200 lines.

Probably no need to fix it since Scrutinizer's first example in post #5 is a correct implementation of the same approach.

Regards,
Alister

---------- Post updated at 06:28 PM ---------- Previous update was at 06:26 PM ----------

With regard to all of the AWK suggestions, without knowing exactly how the script is to be used, it's possible that all of the recommendations are inadequate. Nearly every awk srand implementation's default seed is the number of seconds since the epoch. Successive or simultaneous runs could yield identical results. May or may not be an issue. We don't have sufficient information to make that determination. Just a head's up for the OP.

If it is an issue, more information would be required to determine a robust seed expression.

Regards,
Alister
This User Gave Thanks to alister For This Post:
 

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IMAGECOLORRESOLVE(3)							 1						      IMAGECOLORRESOLVE(3)

imagecolorresolve - Get the index of the specified color or its closest possible alternative

SYNOPSIS
int imagecolorresolve (resource $image, int $red, int $green, int $blue) DESCRIPTION
This function is guaranteed to return a color index for a requested color, either the exact color or the closest possible alternative. If you created the image from a file, only colors used in the image are resolved. Colors present only in the palette are not resolved. PARAMETERS
o $ image -An image resource, returned by one of the image creation functions, such as imagecreatetruecolor(3). o $red -Value of red component. o $green -Value of green component. o $blue -Value of blue component. RETURN VALUES
Returns a color index. EXAMPLES
Example #1 Using imagecoloresolve(3) to get colors from an image <?php // Load an image $im = imagecreatefromgif('phplogo.gif'); // Get closest colors from the image $colors = array(); $colors[] = imagecolorresolve($im, 255, 255, 255); $colors[] = imagecolorresolve($im, 0, 0, 200); // Output print_r($colors); imagedestroy($im); ?> The above example will output something similar to: Array ( [0] => 89 [1] => 85 ) SEE ALSO
imagecolorclosest(3). PHP Documentation Group IMAGECOLORRESOLVE(3)
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