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From: maart@cs.vu.nl (Maarten Litmaath)
Newsgroups: comp.unix.questions
Subject: Re: Problem with getuid() -- same as geteuid()?!
Message-ID: <5315@star.cs.vu.nl>
Date: 6 Feb 90 15:38:41 GMT
References: <1836@clyde.concordia.ca> <?_3}%-@rpi.edu> <1837@clyde.concordia.ca>
Sender: news@cs.vu.nl
Reply-To: maart@cs.vu.nl (Maarten Litmaath)
Organization: VU Informatika, Amsterdam, the Netherlands
Lines: 53

In article <1837@clyde.concordia.ca>,
	smw@maxwell.Concordia.CA ( Steven Winikoff ) writes:
\In article <?_3}%-@rpi.edu> tale@cs.rpi.edu (David C Lawrence) writes:
\
\>@opinionated sidebar
\>I personally loathe getlogin() and programmes that are concerned with
\>what userid I might have started out as on some pre-su level, [...]
\...
\My problem is that there are several people at our site who are legitimately
\able to su root, working on different projects at the same time (perhaps 
\that's a bad idea, but it's not under my control).  In any case, the idea
\is to find some way to identify our printed output, [...]

But that's precisely what UCB's lpr does!  By means of getlogin()! :-(
Anyway, you could always replace lpr by something like this:

	#include	<pwd.h>
	#include	<stdio.h>

	char	My_lpr[] = "/path/of/my_lpr";

	main(argc, argv)
	int	argc;
	char	**argv;
	{
		char	*getenv(), *lprname = getenv("LPRNAME");
		struct	passwd	*pw;

		if (lprname) {
			if (!(pw = getpwnam(lprname)))
				fprintf(stderr,
					"You don't exist.  Go away.\n");
			else if (setuid(pw->pw_uid) != 0)
				perror("setuid");
		}
		argv[0] = My_lpr;
		execv(My_lpr, argv);
		perror(My_lpr);
		exit(1);
	}

...where `my_lpr' is:

	#!/bin/sh 

	exec 3>&1

	test -t 0 && exec < /dev/null

	(/usr/ucb/lpr ${1+"$@"} | cat >&3) 2>&1 | cat >&2
--
  The meek get the earth, Henry the moon, the rest of us have other plans.  |
  Maarten Litmaath @ VU Amsterdam:  maart@cs.vu.nl,  uunet!mcsun!botter!maart