Path: utzoo!utgpu!water!watmath!clyde!bellcore!decvax!ucbvax!pasteur!ames!ll-xn!mit-eddie!husc6!cmcl2!brl-adm!umd5!uvaarpa!mcnc!rti!sas!toebes
From: toebes@sas.UUCP (John Toebes)
Newsgroups: comp.sys.amiga
Subject: Re: getenv() -- Lattice 4.0
Summary: Of course it is ANSI compatible :-)
Keywords: getenv, stdlib.h, Lattice
Message-ID: <334@sas.UUCP>
Date: 17 Feb 88 12:35:38 GMT
References: <6893@agate.BERKELEY.EDU>
Organization: SAS Institute Inc.,Cary NC,25712
Lines: 47

In article <6893@agate.BERKELEY.EDU>, pete@violet.berkeley.edu writes:
> In a recent posting, David Roch [roch@b.uiuc.edu] asked:
>   >  While looking through the include files for Lattice 4.0, I noticed
>   >  that getenv is defined in stdlib.h.  Curious, I tried accessing
>   >  the environment variables set by assign, both with and without
>   >  the colon, but in each case the null string was returned.
> OK -- you got me curious, so I did some code disassembly...
> You're right [strangely...!] in that getenv searches the Device List for
> names.  However, what's returned is NOT another character string (despite
> the prototype in stdlib.h!), but the ADDRESS of the relevant DevInfo block.
> (It can be any device -- not just assigned ones.)
> 
> I wonder what Lattice intends this for?  You can of course use it just
> to test if a device is "mounted"  (just like Bryce and others have done).
> Why use the name "getenv" though?  ...Not exactly ANSI compatible!
Actually it is quite ANSI compatible (in a sense).  To quote the standard:
    Description
        the getenv function searches an environment list, provided by the
    host environment, for a string that matches the string pointed to by name.
    The set of environment names and the method for altering the environment
    list are implementation-defined.

    Returns
        The getenv function returns a pointer to a string associated with the
    matched list member.  The array pointed to shall not be modified by the
    program, but may be overwritten by a subsequent call to the getenv
    function.  If the specified name cannot be fount, a null pointer is
    returned.

Since the description requires the environment list to be provided by the
host environment and we wish to follow the Amiga standards, the appropriate
place to get the information is from the list of assigns.  When an alternative
to this is provided by Commodore as a standard defined interface we would
certainly look toward that.  However since this is what is to be done, 
we must return an indicator of whether or not the item exists.  Note that
ANSI imposes no restrictions on the format of the information returned.
You have the ability to cast the pointer to a DevInfo structure and get
additional information out of the return value.

It's best use is for testing whether something is mounted, but there
are other possibilities.  (Testing for the presence of a configuration
file by name).

/*---------------------All standard Disclaimers apply---------------------*/
/*----Working for but not officially representing SAS or Lattice Inc.-----*/
/*----John A. Toebes, VIII             usenet:...!mcnc!rti!sas!toebes-----*/
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