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Full Discussion: Need shell script to read two file at same time and print out in single file
Top Forums Shell Programming and Scripting Need shell script to read two file at same time and print out in single file Post 302295465 by ripat on Sunday 8th of March 2009 12:18:08 PM
Old 03-08-2009
Quote:
Originally Posted by mjd_tech
Hopefully, this is a correct explanation.
That's exactly it.
Quote:
Originally Posted by mjd_tech
I was initially confused by the _[NL] thing, thinking this was some kind of special awk reserved variable or something, but then I realized it's just an array named _
_ has no special meaning. It's just a fast and, I confess, obfuscated way of writing array names.

Quote:
Originally Posted by mjd_tech
I guess that if file1 were super huge, you could run out of memory because it gets loaded into an array. There's probably a way to do this in perl that can handle huge files without slurping into an array...
Well, maybe. However, awk never hit the memory barrier on my systems even on large test files (1 Mega lines and more). But you are probably right. You could do that by parallel looping through two file handles in perl.
 

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LEARN ABOUT XFREE86

ppmtopgm

ppmtopgm(1)						      General Commands Manual						       ppmtopgm(1)

NAME

       ppmtopgm - convert a portable pixmap into a portable graymap

SYNOPSIS

       ppmtopgm [ppmfile]

DESCRIPTION

       Reads  a  portable  pixmap  as  input.  Produces a portable graymap as output.  The output is a "black and white" rendering of the original
       image, as in a black and white photograph.  The quantization formula used is .299 r + .587 g + .114 b.

       Note that although there is a pgmtoppm program, it is not necessary for simple conversions from pgm to ppm , because any  ppm  program  can
       read  pgm  (and	pbm  ) files automatically.  pgmtoppm is for colorizing a pgm file.  Also, see ppmtorgb3 for a different way of converting
       color to gray.  And ppmdist generates a grayscale image from a color image, but in a way that makes it easy to differentiate  the  original
       colors, not necessarily a way that looks like a black and white photograph.

QUOTE

       Cold-hearted orb that rules the night
       Removes the colors from our sight
       Red is gray, and yellow white
       But we decide which is right
       And which is a quantization error.

SEE ALSO

       pgmtoppm(1),ppmtorgb3(1),rgb3toppm(1),ppmdist(1),ppm(5),pgm(5)

AUTHOR

       Copyright (C) 1989 by Jef Poskanzer.

								   10 April 2000						       ppmtopgm(1)
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