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Top Forums Shell Programming and Scripting for loop with multiple variables ? Post 47500 by fosterian on Wednesday 11th of February 2004 05:38:15 PM
Old 02-11-2004
for loop with multiple variables ?

I have a script which selects two 'sets' of system LVM device files from a tabular file 'mapfile' using awk :

LIVELV=`awk '{print($1)}' mapfile`
BCVLV=`awk '{print($3)}' mapfile`

I wanted to pass these 'sets' into an LVM command 'loop' along the lines of :

lvmerge $BCVLV $LIVELV

ie. for each device file in column 1 of the file 'mapfile' merge in the device in column 3 of the same line.

I have messed about for hours with a for loop but I don't think this will handle the two different sets of variables in the same statement ?

I am probably approaching this from completely the wrong angle.

Any advice would be gratefully received - scripting isn't my strong suit - but god knows I'm trying !
 

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ppmquant(1)                                                   General Commands Manual                                                  ppmquant(1)

NAME
ppmquant - quantize the colors in a portable pixmap down to a specified number SYNOPSIS
ppmquant [-floyd|-fs] ncolors [ppmfile] ppmquant [-floyd|-fs] [-nofloyd|-nofs] -mapfile mapfile [ppmfile] All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one to designate an option. You may use either white space or equals signs between an option name and its value. DESCRIPTION
pnmquant is a newer, more general program that is backward compatible with ppmquant. ppmquant may be faster, though. Reads a PPM image as input. Chooses ncolors colors to best represent the image, maps the existing colors to the new ones, and writes a PPM image as output. The quantization method is Heckbert's "median cut". Alternately, you can skip the color-choosing step by specifying your own set of colors with the -mapfile option. The mapfile is just a ppm file; it can be any shape, all that matters is the colors in it. For instance, to quantize down to the 8-color IBM TTL color set, you might use: P3 8 1 255 0 0 0 255 0 0 0 255 0 0 0 255 255 255 0 255 0 255 0 255 255 255 255 255 If you want to quantize one image to use the colors in another one, just use the second one as the mapfile. You don't have to reduce it down to only one pixel of each color, just use it as is. If you use a mapfile, the output image has the same maxval as the mapfile. Otherwise, the output maxval is the same as the input maxval, or less in some cases where the quantization process reduces the necessary resolution. The -floyd/-fs option enables a Floyd-Steinberg error diffusion step. Floyd-Steinberg gives vastly better results on images where the unmodified quantization has banding or other artifacts, especially when going to a small number of colors such as the above IBM set. How- ever, it does take substantially more CPU time, so the default is off. -nofloyd/-nofs means not to use the Floyd-Steinberg error diffusion. This is the default. REFERENCES
"Color Image Quantization for Frame Buffer Display" by Paul Heckbert, SIGGRAPH '82 Proceedings, page 297. SEE ALSO
pnmquant(1), ppmquantall(1), pnmdepth(1), ppmdither(1), ppm(5) AUTHOR
Copyright (C) 1989, 1991 by Jef Poskanzer. 12 January 1991 ppmquant(1)
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