Problem with getuid() -- same as geteuid()?!

[Steven Winikoff]

First, my apologies if this gets posted twice.  The first one apparently
vanished into the bit bucket.

In article <5315 at star.cs.vu.nl> maart at cs.vu.nl (Maarten Litmaath) writes:
>In article <1837 at clyde.concordia.ca>,
>	smw at maxwell.Concordia.CA ( Steven Winikoff ) writes:
>\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()! :-(

True.  But if I could use lpr in the first place, none of this would have
arisen... :-)     Fact is that the printer I'm trying to reach is connected
to a CDC Cyber under NOS (CDC's proprietary OS, for those unfamiliar with
Control Data).  The Cyber is connected to a VMS VAX 8550 via JNET, and my Unix
system is connected to the VAX via a MicroVAX running Ultrix!  Are you now as
confused as I am?  If not, all you have to do is reread the above paragraph a
couple of dozen times, and then your head will be spinning just like mine! :-)

No, there's no way I can get a printer closer than that.  :-(

And no, there's no way (at least none that our Powers That Be will agree to
finance!) to bridge the gap between Unix and the Cyber directly.  :-(

So I'm stuck with writing an application that wants to send a file to the VAX
via ftp, along with instructions re what to do with it when it gets there.
A client process on the VAX takes the file and automagically routes it over
the JNET link.  (The VAX/Cyber link is maintained by our local VMS guru.  My
personal VMS knowledge ranges between poor and non-existent.)

That's why I need some reliable way of determining who *really* sent a given
file, simply because I'd like to be able to recognize my own output when I
get it!

When I began all this, I naively thought that getuid would do it for me.
Now I know that it won't.  Based on the suggestions of all the kind people
who have so far responded to me, it seems that the best I can do in the case
where getuid returns 0 is a tiered approach which begins with getlogin and
falls back on logname (== value of $USER) when getlogin fails.

>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

I'm not quite sure I understand your code.  Who sets LPRNAME?  In "my_lpr",
what gets exec'd in line 2?  Please excuse my ignorance, I'm only a wizard
wanna-be!

>--
>  The meek get the earth, Henry the moon, the rest of us have other plans.  |
>  Maarten Litmaath @ VU Amsterdam:  maart at cs.vu.nl,  uunet!mcsun!botter!maart

Love your .sig!

------------------------------------------------------------------------
Steven Winikoff                                 smw at maxwell.concordia.ca
Software Analyst
Concordia University Computer Centre            voice: (514) 848-7619
Montreal, Quebec, Canada                               (10:00-18:00 EST)