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Full Discussion: displaying nth line of a file dynamically
Top Forums Shell Programming and Scripting displaying nth line of a file dynamically Post 302451005 by deanamrita on Sunday 5th of September 2010 08:22:45 AM
Old 09-05-2010
displaying nth line of a file dynamically
Hi,

I have a file split.txt with the following contents

Code:
one
two
three
four
five

Suppose if i want to display contents of line 3, I know this could be achieved using the command
Code:
sed -n '3p' split.txt

But I need the line number to be decided dynamically like
Code:
a=3
sed -n '$ap' split.txt

But the above command doesnt work as sed -n '3p' split.txt. So how could I display the contents of a line whose line number is decided dynamically (or) how could I display the contents of a file using line numbers
Last edited by Scott; 09-05-2010 at 09:29 AM.. Reason: Please use code tags
 

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LEARN ABOUT OSX

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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