Random seed each compilation in XeLaTeX

Question

I've found two answers for ``How to get a new PGF seed each compilation?'' 1 2, and they work wonderfully on PdfLaTeX.

However, neither of the methods work on XeLaTeX. I get the error

! Undefined control sequence.
<argument> \number \pdfrandomseed
l.6 \pgfmathsetseed{\number\pdfrandomseed}

when using the first method, and

! Undefined control sequence.
<argument> \pdfuniformdeviate
10000000
l.7 \pgfmathsetseed{\pdfuniformdeviate 10000000}

when using the second. How can these methods be fixed for XeLaTeX use? Is there a particular method for getting a random seed each time in XeLaTeX?

MWE

\documentclass{article}
\usepackage{tikz}
% Two ways to get a new seed every compilation
\pgfmathsetseed{\number\pdfrandomseed} % https://tex.stackexchange.com/a/144623
%\pgfmathsetseed{\pdfuniformdeviate 10000000} % http://tex.stackexchange.com/questions/212738/making-a-random-number
\pgfmathsetmacro\numr{rand}% Print a random number
\begin{document}
\numr
\end{document}

Answer 1

pdfTeX adopted the pdf prefix for most (all?) primitives it introduced, so they are called \pdf<name> even if they have nothing to do with PDF output. In XeTeX these primitives were added in 2019, but they are called only \<name>, so your code becomes (both \randomseed and \uniformdeviate work):

\documentclass{article}
\usepackage{tikz}
% Two ways to get a new seed every compilation
\pgfmathsetseed{\number\randomseed} % https://tex.stackexchange.com/a/144623
% \pgfmathsetseed{\uniformdeviate 10000000} % http://tex.stackexchange.com/questions/212738/making-a-random-number
\pgfmathsetmacro\numr{rand}% Print a random number
\begin{document}
\numr
\end{document}

If you want engine independence, you can use expl3's \sys_rand_seed:. It will work on all engines supported by expl3 (pdfTeX, XeTeX, LuaTex, epTeX and eupTeX):

\documentclass{article}
\usepackage{tikz}
\usepackage{expl3}
\ExplSyntaxOn
\cs_new_eq:NN \RandomSeed \sys_rand_seed:
\ExplSyntaxOff
% Two ways to get a new seed every compilation
\pgfmathsetseed{\RandomSeed} % https://tex.stackexchange.com/a/144623
% \pgfmathsetseed{\uniformdeviate 10000000} % http://tex.stackexchange.com/questions/212738/making-a-random-number
\pgfmathsetmacro\numr{rand}% Print a random number
\begin{document}
\numr
\end{document}