Hi Thierry, On Fri, Jul 28, 2023 at 11:59 AM Joseph Wright <[log in to unmask]> wrote: > > Older LaTeX used \openin + \ifeof to test for file existence; we now use > \(pdf)filesize, which is expandable and reports "0" for a non-existent > file. Both methods should find "foo.tex" from "foo" in the same way. A wild guess: maybe your implementation of |\pdffilesize| doesn't try to guess the extension as |\input| does, thus the difference you are seeing. Because as others have already said, |\input{docstrip}| works in both older and newer (web2c-based) LaTeX. Sorry if this isn't useful: can't run any code right now. Best, Phelype