bibtex::read.bib -- extracting bibentry keys

I have two versions of a bibtex database which have gotten badly out of 
sync. I need to find find all the entries in bib2 which are not 
contained in bib1, according to their bibtex keys. But I can't figure 
out how to extract a list of the bibentry keys in these databases.
read.bib() returns a "bibentry" object so you can simply do this as usual
for "bibentry" objects with $key:

x <- read.bib(...)
x$key

or maybe

unlist(x$key)

Whatever is more convenient for you. See ?bibentry for more details.
A minor question: Is there someway to prevent read.bib from ignoring 
entries that do not contain all required fields?
Also not really an issue with read.bib itself. read.bib() wants to return 
a "bibentry" object but bibentry() just allows to create objects that are 
valid BibTeX, i.e., have all required fields.
A suggestion: it would be nice if bibtex provided some extractor functions 
for bibentry fields.
So that only a subset of fields is read as opposed to all fields?

If you read all fields, you can easily subset afterwards (again using 
$-notation).

hth,
Z
bib1 <- read.bib("C:/localtexmf/bibtex/bib/timeref.bib")
ignoring entry 'Donoho-etal:1988' (line 40) because :
A bibentry of bibtype ?InCollection? has to correctly specify the field(s): 
booktitle
... snipping other similar warnings ...

length(bib1)
[1] 628
bib2 <- read.bib("W:/texmf/bibtex/bib/timeref.bib")
ignoring entry 'Donoho-etal:1988' (line 57) because :
A bibentry of bibtype ?InCollection? has to correctly specify the field(s): 
booktitle
... snipping other similar warnings ...

length(bib2)
[1] 611

# The first bibentry:
bib1[[1]]
Godfrey EH (1918). ?History and Development of Statistics in Canada.? In 
Koren J (ed.), pp.
179-198. Macmillan, New York.
str(bib1[[1]])
Class 'bibentry' hidden list of 1
$ :List of 9
..$ author :Class 'person' hidden list of 1
.. ..$ :List of 5
.. .. ..$ given : chr [1:2] "Ernest" "H."
.. .. ..$ family : chr "Godfrey"
.. .. ..$ role : NULL
.. .. ..$ email : NULL
.. .. ..$ comment: NULL
..$ title : chr "History and Development of Statistics in {Canada}"
..$ booktitle: chr "History of Statistics, their Development and Progress in 
Many Countries"
..$ publisher: chr "Macmillan"
..$ year : chr "1918"
..$ editor :Class 'person' hidden list of 1
.. ..$ :List of 5
.. .. ..$ given : chr "John"
.. .. ..$ family : chr "Koren"
.. .. ..$ role : NULL
.. .. ..$ email : NULL
.. .. ..$ comment: NULL
..$ pages : chr "179--198"
..$ address : chr "New York"
..$ crossref : chr "Koren:1918"
..- attr(*, "bibtype")= chr "InCollection"
..- attr(*, "key")= chr "Godfrey:1918"

So, I try to get the "key" attribute for this entry, but it returns NULL, and 
I don't understand why.
attr(bib1[[1]], "key")
NULL
attr(bib1[1], "key")
NULL

-Michael

-- 
Michael Friendly     Email: friendly AT yorku DOT ca
Professor, Psychology Dept.
York University      Voice: 416 736-2100 x66249 Fax: 416 736-5814
4700 Keele Street    Web:   http://www.datavis.ca
Toronto, ONT  M3J 1P3 CANADA

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bibtex::read.bib -- extracting bibentry keys

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