Question on file owner name representation Post: 302425559

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Top Forums Shell Programming and Scripting Question on file owner name representation Post 302425559 by Corona688 on Friday 28th of May 2010 12:25:54 PM

05-28-2010

Registered User

Quote:

Originally Posted by Arunprasad

I thought the same but in my case, all user s are LDAP and not maintained locally. So how system determines that this user has been deleted and let represent the userid as number. And for your information, still many user directories/files are showing properly with userid/owner name in its properties.

Thanks a lot for your time! Please advise.

It's abstracted behind the getpwent() call and its related calls, looks like:

Code:

GETPWENT(3)                Linux Programmer's Manual               GETPWENT(3)



NAME
       getpwent, setpwent, endpwent - get password file entry

SYNOPSIS
       #include <sys/types.h>
       #include <pwd.h>

       struct passwd *getpwent(void);

       void setpwent(void);

       void endpwent(void);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getpwent(), setpwent(), endpwent(): _BSD_SOURCE || _SVID_SOURCE ||
       _XOPEN_SOURCE > = 500

DESCRIPTION
       The getpwent() function returns a pointer to a structure containing the
       broken-out  fields  of  a  record from the password database (e.g., the
       local password file /etc/passwd, NIS, and LDAP).  The first time it  is
       called  it  returns  the first entry; thereafter, it returns successive
       entries.

...

So ls doesn't reach in and grab login names from /etc/passwd manually, it just calls getpwent() from glibc, which is capable of getting login info from any valid sources. Finding no corresponding UID in either, ls just prints the UID/GID.

Didn't know getpwent() did that. That's a pretty good reason to use these functions instead of just parsing /etc/passwd yourself!

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LEARN ABOUT ULTRIX

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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