Thanks to Alan for his prompt and helpful reply. I suspected that the truth 
might be something like that, but didn't have access to Linux or MacOS in a 
hurry.
Best wishes
Roger
At 00:07 11/10/2005, Alan Riley wrote:
Roger Newson ([email protected]) asked about file extensions
in Stata:
> ...
> What is the algorithm used by Stata to decide whether a filename already
> has an extension? And is it the same for all operating systems? I ask
> because my own program --listtex- can fail when given a filename 
without an
> extension, because it uses both -outfile- and -file-, and I would like to
> fix this bug in a way that doesn't create other bugs in operating
> environments other than Windows 2000 (under which I use Stata 9.1).
> ...
In part of Roger's email which I omitted, he explained that -outfile-
assigns a default extension when none is specified while -file- does not.
Commands in Stata for which there is a default filetype will add
a default extension if necessary.  Examples of such commands are
   use
   save
   insheet
   outsheet
   infile
   outfile
   graph use
   graph save
   log
All such commands work with one main filetype and therefore they can
add a default extension when none is specified.
-file-, on the other hand, is a low-level programmer command.  There
is no default kind of file which -file- reads and writes, and therefore
it is up to the programmer to specify an extension.  One user might
use -file- with .txt files while another user might use -file- with
.dta files.
Stata determines whether or not a file has an extension in the same
way across all operating systems.  It starts at the beginning of
the filename and looks forward for a period.  If one is found,
then Stata determines the file has an extension and will not add
one.
--Alan
([email protected])
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--
Roger Newson
Lecturer in Medical Statistics
Department of Public Health Sciences
Division of Asthma, Allergy and Lung Biology
King's College London
5th Floor, Capital House
42 Weston Street
London SE1 3QD
United Kingdom
Tel: 020 7848 6648 International +44 20 7848 6648
Fax: 020 7848 6620 International +44 20 7848 6620
  or 020 7848 6605 International +44 20 7848 6605
Email: [email protected]
Website: http://phs.kcl.ac.uk/rogernewson/
Opinions expressed are those of the author, not the institution.
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