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Top Forums Shell Programming and Scripting sed and awk to insert a line after a para Post 302901341 by Don Cragun on Tuesday 13th of May 2014 11:59:15 AM
Old 05-13-2014
Quote:
Originally Posted by protocomm
thanks for your explications, i'm not an expert as you, i use always the same OS (OSX) and the same shell (bash 3.2), in my case i think that $var don't modify the contents of file

... ... ...

Thx
Hi protocomm,
Try the following script:
Code:
var=$(awk '1' < file);echo "$var" > file

on OS X using bash when file contains:
Code:
-n

I think you will find that it changes the contents from the three characters -, n, and <newline> to an empty file.

On some other operating systems, much more common file contents could be converted in ways (some obvious and some subtle) that would render working shell scripts or correct C source code contained in file into streams of syntax errors.
 

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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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