Path: utzoo!mnetor!uunet!husc6!ncar!gatech!mcnc!decvax!decwrl!pyramid!prls!philabs!micomvax!zap!iros1!mcgill-vision!mouse
From: mouse@mcgill-vision.UUCP (der Mouse)
Newsgroups: comp.unix.questions
Subject: Re: How does a program get its path name?
Message-ID: <994@mcgill-vision.UUCP>
Date: 13 Mar 88 03:34:41 GMT
References: <11923@brl-adm.ARPA> <2933@sdsu.UUCP>
Organization: McGill University, Montreal
Lines: 25

In article <2933@sdsu.UUCP>, turtle@sdsu.UUCP (Andrew Scherpbier) writes:
> In article <11923@brl-adm.ARPA> Leisner.Henr@xerox.com (marty) writes:
>> How does an exec program get the pathname it was execed from if it
>> wants to find out this information?

In general, it can't.

> When a program executes, the full path to the executable file is kept
> in the zero-th argument.  If you have a declaration of main which
> looks like this:
>	main(argc,argv)	int argc; char *argv[];
> then argv[0] is a pointer to the full path.

Not at all.  argv[0] is merely whatever was passed to the exec-family
routine that executed the program.  The shell conventionally passes
whatever name the program was called by in this field, but this (a) is
not always a full pathname and (b) is not a universal convention in the
first place.  If a program wants, it can run your program and make
argv[0] be "/bin/sh", or "Jan 23 1988, 11:44:82.35 GMT", or whatever it
pleases.

					der Mouse

			uucp: mouse@mcgill-vision.uucp
			arpa: mouse@larry.mcrcim.mcgill.edu