On 29/07/2023 08:29, LARONDE Thierry wrote:
> On Sat, Jul 29, 2023 at 08:15:19AM +0100, Joseph Wright wrote:
>> On 29/07/2023 07:36, LARONDE Thierry wrote:
>>> On Fri, Jul 28, 2023 at 07:53:19PM +0100, David Carlisle wrote:
>>>> On 28/07/2023 18:57, LARONDE Thierry wrote:
>>>>
>>
>>> 1) Is LaTeX expecting to be able to "\input" a file without extension?
>>> For me, "\input" could only be a tex file; so the extension was
>>> mandatory...
>>
>> No. \input is the only way to read a file 'here'. Most obviously, many users
>> reserve .tex for plain TeX files and use .ltx for LaTeX sources. But to have
>> systematic file naming you need different extensions, e.g. LaTeX packages
>> are .sty, classes are .cls, etc., all of which are ultimately used with the
>> \input primitive.
> 
> My problem is not for a file with an extension. But for a file given
> without an extension. Is "\input README" expected to work for a filename
> "README", without an extension, or only with the added ".tex" extension?

TeX first looks for "README.tex", and then if not found for "README". 
This is 'how it is'.

> And from the excerpt given in another message (texmf.cnf), it seems
> that it is allowed to even add a ".tex" to a file with already an
> extension: "a.b.tex"???!!!

Yes, correct: again, standard TeX behaviour.

Joseph