(for real this time): need help with 'execl(3V)'
2007-12-25 7:57:00
attempting to send this summary, but had to abort the message...
unfortunately, the ORIGINAL retransmitted. Please delete it!!!
The solution was staring me in the face the entire time and I missed it...
My original query (for those who like to have the original with the summary):
*****************************************************************************
Running SUNOS 4.1.1b on Sparcstations 1, 1+, 2, IPC, all networked, NIS.
I need some assistance with the 'execl(3V)' command. I am attempting to
write a front-end for 'rlogin' and 'rsh' to restrict their usage to our
local net (I know about group access, but this is an entirely different
problem). The front-end is in C, and my parameter parser works fine.
My problem is when I try to call /usr/ucb/rlogin (haven't gotten to rsh yet)
with 'execl'. My call looks like this:
if ( ok == 'y' )
{
*++argv; /* to remove my program name */
execl("/usr/ucb/rlogin", argv);
}
as specified in the man page. If I send one parameter as in
% myrlogin machinea
everything works fine. If I send any more than one parameter, as in
% myrlogin -8 machinea
I get the usage message from 'rlogin' as if I had sent a wrong parameter.
I have even tried this with the straight 'exec' call and sending exactly the
parameters in the second example and terminating with a null ( (char *)0 ).
That also failed exactly as above.
I even print the parameters I send before sending to make sure that they are
correct.
Any clues? I am at my wit's end on this one.
Please send any replies to me directly and I will summarize.
*****************************************************************************
And here is the summary:
Almost everyone who responded to this point got it right (and also realized
I had made the mistake I pointed out in my earlier message of today), that I
didn't note the significance of argv[0] as HAVING to hold the name of the
program being executed, even though the first parameter of 'execv' was the
name of the ACTUAL program to be executed... The C books I have and the man
page weren't exactly clear on that point, at least not to me. Anyway, this
is the fix:
if ( ok == 'y' )
{
/* *++argv; /* to remove my program name */ <-------------
execl("/usr/ucb/myrlogin", argv);
}
In other words, don't remove argv[0], and rename 'rlogin' to something else,
preferably someWHERE else, with perhaps different privs, etc. I intend to
experiment further with this, but you have gotten me past a problem I would
not have seen the solution to in a hundred years due to the fact that it was
so simple...
Many thanks to the following:
phil@pex.eecs.nwu.edu William LeFebvre
del+@cmu.edu Daniel Edward Lovinger
schwartz@groucho.cs.psu.edu Scott Schwartz
chris@rufus.state.com.au Chris Keane
tom@sees.bangor.ac.uk Tom Crummey
rackow@anteres.mcs.anl.gov Gene Rackow (thanks for the security docs!)
mwallen@ucsd.edu Mark R Wallen
poul@nulu.no Poul Sorensen (thanks for the detail!)
Joel L. Seber | Dry humor is wasted around here.
SUN Workstation Laboratory Manager |
Center for Manufacturing Research | -Joel L. Seber
and Technology Utilization |
Tennessee Technological University | recursive, adj.
Cookeville, TN 38505 | See 'recursive'
|
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