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Full Discussion: Honey, I broke awk! (duplicate line removal in 30M line 3.7GB csv file)
Top Forums Shell Programming and Scripting Honey, I broke awk! (duplicate line removal in 30M line 3.7GB csv file) Post 302894671 by DGPickett on Wednesday 26th of March 2014 04:07:49 PM
Old 03-26-2014
If I recall correctly, cygwin and win7 not -64 is 32 bit, so 'a' may get too big for the address space of the awk process. Depending on ram size, it might eventually thrash a bit. The awk solution, a hash map, does not support parallism.

The classic, robust solution is 'sort -u <file_set>' but tends to be slower. You can parallelize the sort with a command of the form:
Code:
sort -mu <( sort -u <file_set_1> )  <( sort -u <file_set_2> ) <( sort -u <file_set_3> ) . . . .

where the nicer ksh or bash makes named pipes of the '<(...)' that run concurrently. I like twice the core count <(sort)'s, assuming 50% i/o delay. The final pass of the <(sort)'s feeds the sort -m merge parent.

ETL programs like Ab Initio know how to tell parallel processes to split up big files and process each part separately, even when the files are linefeed delimited (they all agree to search up (or down) for the dividing linefeed closest to N bytes down file). Does anyone know of a utility that can split a file this way (without reading it sequentially)? 'GNU parallel?'
 

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LEARN ABOUT OPENSOLARIS

ppmhist

ppmhist(1)                                                    General Commands Manual                                                   ppmhist(1)

NAME

       ppmhist - print a histogram of a portable pixmap

SYNOPSIS

       ppmhist [-hexcolor] [-noheader] [-map] [-nomap] [-sort={frequency,rgb}] [ppmfile]

DESCRIPTION

       Reads  a  PPM  image as input.  Generates a histogram of the colors in the image, i.e. a list of all the colors and how many pixels of each
       color are in the image.

OPTIONS

       -sort={frequency,rgb}
              The -sort option determines the order in which the colors are listed in the output.  frequency means to list them in  order  of  how
              pixels  in the input image have the color, with the most represented colors first.  rgb means to sort them first by the intensity of
              the red component of the color, the of the green, then of the blue, with the least intense first.

              The default is frequency.

       -hexcolor
              Print the color components in hexadecimal.  Default is decimal.

       -noheader
              Do not print the column headings.

       -map   Generates a PPM file of the colormap for the image, with the color histogram as comments.

       -nomap Generates the histogram for human reading.  This is the default.

SEE ALSO

       ppm(5), pgmhist(1), ppmtomap(1), pnmhistmap(1), ppmchange(1)

AUTHOR

       Copyright (C) 1989 by Jef Poskanzer.

                                                                 17 September 2000                                                      ppmhist(1)
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