Re: Minutes of the 9th March 2017 Teleconference

2017-03-10 Thread Robert Elz 
Date:Fri, 10 Mar 2017 12:12:57 +
From:Andrew Josey 
Message-ID:  <90d2058a-5014-4f9c-95f9-51dba40af...@opengroup.org>

  | Bug 0001038: Specification relies upon unspecified behaviour OPEN
  | http://austingroupbugs.net/bug_view_page.php?bug_id=1038
  | 
  | The whole call was spent on this item.

Actually, it seems that more time might have been spent on the issue of
what the default PS1 should be (and what it means if it becomes unset)
none of which is really that item.

  | We have a proposed change to the "$ " problem in the etherpad,

Looks fine to me.   I might have just added a new bullet to the list,
but either way is fine.

Some comments about text I see on the etherpad...

Mark:
] Suggested change:
]At page 2352 line 74952 change:
]The default value shall be "$ ".
]to:
]The default value shall be '$ '.

That actually changes nothing - the quotes in that are a typographical
convention in the doc to show that the default value of PS1 is the two
character sequence dollar space, they're not intended to be sh syntax quotes.

The 2 character sequence is still subject to parameter expansion, whatever
format the value is represented in the text as.   It might make a difference
of the text said something more like
The default shall be as if the command PS1="$ " were executed.
but it doesn't (and there is no real point rewording it that way.)

Mark:
] How about: The default value of PS1 should be defined in a way that
] results in '$ ' to be displayed?

That's not good enough, I need to know how to set it explicitly, not just
that the shell can implement some internal magic that makes this happen.

What's more I need to safely be able to do
PS1="my-string${PS1}"
and know that's safe - that nothing that happens to be in "my-string" can
affect the (embedded) expansion of PS1 - for that I need to know what the
initial value of PS1 will be.

Mark:
] Each time an interactive shell is ready to read a command, the value
] of this variable shall be subjected to parameter expansion and written
] to standard error.
]
] I read this as the intent being: if it is unset, so can't be evaluated, ...

That would be bizarre - it is perfectly OK (and done all the time) to
evaluate unset variables - the result is just a null string, nothing
special is needed to handle this case.   It really is no different than
unsetting PATH - the shell has to evaluate $PATH to perform command lookup
for all commands not containing a / (and not being special builtins...)
Yet no-one believes that "unset PATH" means that PATH gets magically reset
to its default value when it is needed.   As far as I'm aware, only IFS
is somewhat special in this regard, and only sometimes (and when that happens
it is made very clear.)

I agree that some text could be added to explain the startup sequence better,
where the initial values of the shell variables (of which PS1 is just one)
and how they come about, is better defined.

Probably this belongs in 2.5.3, possibly by changing line 74898 from

   The following variables shall affect the execution of the shell:

to something more like

The variables listed below shall affect the execution of the shell.
Where an initial (or default) value is specified, that value shall
be assigned to the variable during shell initialization, before the
environment is examined, which may then supply different values.
Subsequently (including while processing the script given by 
ENV,
when such processing occurs) these variables can be updated, or unset,
as with any other variable. Except as noted no other special
processing takes place if that  occurs (default values are not
re-instated into unset variables.)

It might also be worth noting with IFS that it is unspecified whether its
value can be obtained from the environment (some shells do not allow that.)


And most importantly (and back on issue 1038) ...

Mark:
]  Does anyone disagree with below, as our operating presumption:
]Re: 3606
]Parameter and other Expansions happen on tokens, not text.

I do.   Or I do unless by this you mean that a double-quoted string,
or a here document text, can be called a word token (which is what it
would be - at least strings - when lexically scanned before parsing)
but if that is what you mean then it doesn't really help anything.

On the other hand, if you mean that strings, here docs, etc, should be
tokenised (according to 2.3) as a first step as part of performing the
various expansions permitted (or required) then that's simply wrong.

"tokens" as a notion only make sense as input to the parser - they are the
input symbols to the grammar, they have no meaning, or use, in other contexts.

The test in processing step 5 of section 2.3 that relates to $ processing,
is so that tokens will be correctly recognised, that is so that

x=$(echo

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meeting.ics
Description: application/ics

Minutes of the 9th March 2017 Teleconference

2017-03-10 Thread Andrew Josey 
All

Enclosed are the minutes from this weeks call.
The next call is on the 16th.  The US clocks will have changed, so it will be an
hour earlier in Europe.

regards
Andrew


Minutes of the 9th March 2017 Teleconference Austin-805 Page 1 of 1
Submitted by Andrew Josey, The Open Group. 10th March 2017

Attendees:
Don Cragun, IEEE PASC OR
Mark Ziegast, SHware Systems Dev.
Nick Stoughton, USENIX, ISO/IEC JTC 1/SC 22 OR
Joerg Schilling, FOKUS Fraunhofer
Geoff Clare, The Open Group
David Clissold, IBM
Martin Rehak, Oracle, The Open Group OR
Eric Blake, Red Hat
 
Apologies
Richard Hansen, Google 
Andrew Josey, The Open Group

* General news 

The draft PAR has not yet been submitted. Don and others had provided feedback 
by email.


* Outstanding actions

( Please note that this section has been flushed to shorten the minutes -
to locate the previous set of outstanding actions, look to the minutes
from 28 Jan 2016)

Bug 249: Add standard support for $'...' in shell   Reopened
http://austingroupbugs.net/bug_view_page.php?bug_id=249
We will return to bug 249 on a future call.

Bug 953: Alias expansion is under-specified   Was Accepted as Marked
http://austingroupbugs.net/view.php?id=953
Richard has an action to propose new wording to discuss in a future telecon.

* Current Business


Bug 0001038: Specification relies upon unspecified behaviour OPEN
http://austingroupbugs.net/bug_view_page.php?bug_id=1038

The whole call was spent on this item.
We have a proposed change to the "$ " problem in the etherpad, and
Don took an action to propose additional changes to the PS1 description
for Issue 8 (to be applied after the changes in bug 1006).

To be continued next week

Next Steps
--
The next call is on March 16th, 2017 (a Thursday)

Calls are anchored on US time. (8am Pacific) 
Note that due to US daylight savings time, it will be one hour earlier in 
Europe.

Apologies in advance from
Eric Blake
David Clissold

This call will be for the regular 90 minutes.

http://austingroupbugs.net

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An etherpad is usually up for the meeting, with a URL using the date format as 
below:

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password=2115756#


Andrew JoseyThe Open Group
Austin Group Chair  
Email: a.jo...@opengroup.org 
Apex Plaza, Forbury Road,Reading,Berks.RG1 1AX,England
Tel:+44 118 9023044