This iftex package provides a suite of commands for detecting different TeX variants.
For each supported engine, tests are provided of the form
\ifpdftex which is true if PDFTeX is in use and \RequirePDFTeX
which stops the run with an error message if PDFTeX is not being used.
The package (which works with plain TeX as well as LaTeX) has tests for:
eTeX, PDFTeX, XeTeX, LuaTeX, LuaHBTeX, pTeX, upTeX, pTeX-ng, VTeX, Aleph, TexpadTeX, HiTeX, LuaMetaTeX.
In addition, an \iftutex test is true for XeTeX and LuaTeX, and
an \ifpdf test is provided to test the PDF or DVI output mode.
In addition to the main iftex.sty package, small wrapper packages are
provided
ifetex.sty ifluatex.sty ifvtex.sty ifxetex.sty ifpdf.sty
These include iftex and in some cases emulate some additional commands to allow these packages to replace the original packages in TeX distributions. It is recommended that new documents do not use these packages, but instead load iftex.sty directly.
This package may be used on any format (it may be loaded into initex) it does not assume LaTeX.
This is a merger and simplification of several packages, based on a suggestion of Norbert Preining.
ifetex: Martin Scharrerifxetex: Will Robertsoniftex: Persian TeX Group / Vafa Khalighiifluatex,ifvtex: Heiko Oberdiekifptex: Takayuki Yatoifpdf: Heiko Oberdiek and LaTeX3 Project
The existing if(u)ptex packages do far more extensive testing to distinguish different variants which are not copied here.
A document specifically for Japanese texts may need the finer grained tests of the ifptex package which has tests for particular versions of the pTeX (Japanese TeX) variant in use, and for the mode that is active.
This generic package only has coarser tests for the tex variant in use, so is sufficient for example to distinguish upTeX from pTeX, and to distinguish both of those from LuaTeX.