=== iftex package ===
{{{
\usepackage{iftex}
}}}

{{{
\ifPDFTeX
...
\else
...
\fi
}}}

{{{
\ifXeTeX
...
\else
...
\fi
}}}

{{{
\ifLuaTeX
...
\else
...
\fi
}}}

{{{
\RequirePDFTeX
\RequireXeTeX
\RequireLuaTeX
}}}

XeTeX°ú PDFTeX¿¡¼­ ÇÑ±Û ¼³Á¤ µî ¿¹½Ã
{{{#!vim tex
\usepackage{iftex}
\usepackage{kotex} %%% kotexÀº pdftex/xetex/luatex ¿£Áø¿¡ µû¶ó ¼³Á¤ÀÌ ¹Ù²ï´Ù.

\ifXeTeX
 \defaultfontfeatures{Mapping=tex-text}
 \setmainfont{Times New Roman}
 \setmainhangulfont{Batang}
% <.... ±âŸ XeTeXÀÇ ¼³Á¤>
\else\ifPDFTeX
 \usepackage{graphicx}
% <.... ±âŸ PDFTeXÀÇ ¼³Á¤>
\fi\fi
}}}
=== ifxetex, ifluatex package ===
{{{
\usepackage{ifxetex}
\ifxetex
...
\else
...
\fi
}}}

{{{
\usepackage{ifthen,ifxetex}
\ifthenelse{\boolean{xetex}}{..<true>..}{..<false>..}
}}}

{{{
\usepackage{ifluatex}
\ifluatex
...
\else
...
\fi
}}}

=== ifpdf package ===
{{{
\usepackage{ifpdf}
\ifpdf
...
\else
...
\fi
}}}