[Patches] [ python-Patches-460805 ] Support for unsetenv()

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Patches item #460805, was opened at 2001-09-11 21:25
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Category: Library (Lib)
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Chris Gonnerman (solomoriah)
Assigned to: Nobody/Anonymous (nobody)
Summary: Support for unsetenv()

Initial Comment:
The attached patch files implement os.unsetenv() for 
Python 2.1 and 2.2a3.  os.py is extended to call 
unsetenv() when _Environ.__delitem__ is called.


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>Comment By: Guido van Rossum (gvanrossum)
Date: 2001-09-12 18:31

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Code bloat. If it's not important enough to standardize in
POSIX (or one of the other standards), why should we add it?
GNU code is infamous for always including more features,
needed or not. If you're cynical, this is part of a
Microsoft-like "buy-in" strategy (code developed for GNU
libc doesn't work anywhere else).

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Comment By: Chris Gonnerman (solomoriah)
Date: 2001-09-12 18:20

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By the way, I found the following note in the man pages
for NetBSD:

    The functions setenv() and unsetenv() appeared in 
    Version 7 AT&T UNIX.

so it appears, standard or not, that most real Unix systems
should have it.

Regarding the minimal utility argument, I don't currently
have a use for it, but it came up on the mailing list
so I wrote it.  It's recommended, when writing sysadmin
tools which call other programs, to "clean up" the 
environment so that only known-safe values are in there
before calling the externals.



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Comment By: Chris Gonnerman (solomoriah)
Date: 2001-09-12 18:14

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Well, the only place I know of that it is standardized is 
in GNU libc.  That's not entirely the point, though.

1) If you do 'del os.environ["SOMEVAR"]' you remove SOMEVAR 
from the copy of the environment but not from the real 
environment.  This behavior IMHO is broken.

2) It's true, many OS's don't have unsetenv().  However, 
my patch falls back to the *current* behavior if unsetenv()
is not available.  In other words, this doesn't break 
Python any more than it's already broken, and it's a net
gain for operating systems that *do* have unsetenv().

I figure if some gain and none lose, why not do it?


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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-09-12 06:38

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Can you point to where unsetenv is standardized? I'm worried
that it's not available on standard-conforming Unix systems,
and since it's of marginal utility at best, I'm not sure
what the point is to add it -- unless there's a clear
standard that ensures its existence.

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