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Top Forums Shell Programming and Scripting Question on file owner name representation Post 302425227 by Corona688 on Thursday 27th of May 2010 11:06:44 AM
Old 05-27-2010
It's quite possible to have files belonging to users or groups with no corresponding entry in /etc/passwd or /etc/group, nothing prevents it. Anything with sufficient privileges can create files belonging to any ID and group whether represented by anything in passwd or group or not; those only control login permissions through the traditional login system.
Code:
touch this ; sudo chown 9999 this

All users and groups are just numbers anyway. If ls doesn't find matching entries in passwd and/or group it will just display numbers. As long as whatever login manager involved sets correct access permissions on login based on the relevant user and group numbers, and the numbers used internally and externally don't overlap, things can be kept consistent without knowing all names locally.

Last edited by Corona688; 05-27-2010 at 12:17 PM..
 

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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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