Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!rutgers!labrea!decwrl!sun!gorodish!guy
From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: Accessing argc & argv from a functi
Message-ID: <24333@sun.uucp>
Date: Tue, 28-Jul-87 14:38:53 EDT
Article-I.D.: sun.24333
Posted: Tue Jul 28 14:38:53 1987
Date-Received: Thu, 30-Jul-87 02:34:29 EDT
References: <420@sugar.UUCP> <39@flmis06.ATT.COM>
Sender: news@sun.uucp
Lines: 40

> >> In standard C you cannot get access to argv/argc/envp without doing work
> >> in main().
> > 
> > getenv()? putenv()? execl()? execv()? execlp()? execvp()?
> 
> Sure, all of the above access the enviorment in one way or another.
> 
> However I am still looking for a way to get at "argc" and "argv" from
> a function when I don't have access to "main". getenv() and putenv()
> gets it from somewhere...

No, "getenv" and "putenv" get at *envp*; they don't look at "argv" or "argc"
at all.  In UNIX C implementations, at least, there is a global
variable "environ", to which the value of "envp" is assigned by the C
startup code.

Note, however, that if we're truly talking about "standard" C, there
isn't even a guarantee that "argv", "argc", or "envp" even *exist*!
According to the current ANSI C draft, in a "freestanding
environment" (where the C program may be run "without any benefit of
an operating system"), "the name and type of the function called at
program startup are implementation-defined".

In a "hosted environment", the function in question is called "main";
I infer from the description that the function is guaranteed to be
called with two arguments, "argc" and "argv" (it says the function
can be defined with no parameters, or with the usual two parameters,
which I assume means either is valid in any hosted environment).  The
"envp" argument is listed only in Appendix A, under "Common
extensions".

> As far as the rest of the above mentioned functions, you will need to
> have the args (or at least create your own) first, before you can pass
> them on...

Arguments yes, environment no.  Those routines get the environment
from "environ".
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com