Getting Texlive version in pdflatex?

Question

I just installed Texlive 2014, and ran into this problem: lgrxenc.def not nound. The solution is apparently to remove LGRx from \usepackage[LGRx,T1]{fontenc}; but I'd rather use something like this:

\ifnum \texliveVersion<2013
  \usepackage[LGRx,T1]{fontenc}
\else
  \usepackage[T1]{fontenc}
  \usepackage[greek,english]{babel}
\fi

Anything like this out there, which would not require me to run -shell-escape everytime - just in case I need to compile the same document on the machine that has earlier TexLive?

---

EDIT: this is what I meant - this should be the code in https://tex.stackexchange.com/a/191705/2595 , but with a conditional switch for Texlive2014; unfortunately it crashes with ! Undefined control sequence. l.50 ...\bbl@monogreek \bbl@monogreek=\l@monogreek:

\documentclass[a4paper]{article}

% https://tex.stackexchange.com/a/16794/2595

\begingroup\makeatletter\endlinechar=\m@ne\everyeof{\noexpand}
\edef\x{\endgroup\def\noexpand\TeXLiveVersion{\@@input|"pdflatex -version | awk '/TeX Live/{print substr($5, 0, length($5)-1);}'" }}\x

\typeout{TexLive version is: \TeXLiveVersion}

% https://tex.stackexchange.com/a/191705/2595

\ifnum\TeXLiveVersion<2014 %
  \typeout{TexLive version is smaller than 2014, using LGRx} %
  \usepackage[LGRx,T1]{fontenc} %
\else %
  \typeout{TexLive version is >= 2014, NOT using LGRx} %
  \usepackage[T1]{fontenc} %
\fi %

% \usepackage{xgreek}
\usepackage[utf8x]{inputenx}
\usepackage[english,greek]{babel}

\begin{document}

The starting verse of the Iliad is
\begin{quotation}\greektext
Μῆνιν ἄειδε, θεά, Πηληιάδεω Ἀχιλῆος
\end{quotation}
and it's really great.

\end{document}

Answer 1

This works with pdflatex and lualatex.

\documentclass{article}

\def\gettexliveversion#1(#2 #3 #4#5#6#7#8)#9\relax{#4#5#6#7}
\edef\texliveversion{\expandafter\gettexliveversion\pdftexbanner\relax}

\ifnum\texliveversion<2013
  \usepackage[LGRx,T1]{fontenc}
\else
  \usepackage[T1]{fontenc}
\fi
\usepackage[greek,english]{babel}

Tested on a “vanilla TeX Live” and also on a Debian provided one.

Explanation: \pdftexbanner expands to

This is pdfTeX, Version 3.14159265-2.6-1.40.15 (TeX Live 2014) kpathsea version 6.2.0

on a vanilla TeX Live, but to

This is pdfTeX, Version 3.14159265-2.6-1.40.15 (TeX Live 2014/Debian) kpathsea version 6.2.0

on Debian TeX Live (and similarly for other packaged distributions). The \gettexliveversion macro gets as its first argument everything up to (; #2 is TeX, #3 is Live, #4#5#6#7 is the year, #8 everything up to the ) and #9 is the rest. One might also use #8 for other purposes, so I left it there instead of gobbling everything after the year.

Alternative (and easier) version:

\IfFileExists{lgrxenc.def}
  {\usepackage[LGRx,T1]{fontenc}}
  {\usepackage[T1]{fontenc}}

---

Test 1

\documentclass{article}

\def\gettexliveversion#1(#2 #3 #4#5#6#7#8)#9\relax{#4#5#6#7}
\edef\texliveversion{\expandafter\gettexliveversion\pdftexbanner\relax}

\ifnum\texliveversion<2013
  \usepackage[LGRx,T1]{fontenc}
\else
  \usepackage[T1]{fontenc}
\fi

\usepackage[utf8]{inputenc}
\usepackage[greek,english]{babel}

\begin{document}

The starting verse of the Iliad is
\begin{quotation}\greektext
Μῆνιν ἄειδε, θεά, Πηληιάδεω Ἀχιλῆος
\end{quotation}
and it's really great.

\end{document}

Test 2

\documentclass{article}

\IfFileExists{lgrxenc.def}
  {\usepackage[LGRx,T1]{fontenc}}
  {\usepackage[T1]{fontenc}}

\usepackage[utf8]{inputenc}
\usepackage[greek,english]{babel}

\begin{document}

The starting verse of the Iliad is
\begin{quotation}\greektext
Μῆνιν ἄειδε, θεά, Πηληιάδεω Ἀχιλῆος
\end{quotation}
and it's really great.

\end{document}

Both test tried with TeX Live 2012 and 2014. The output is always the same:

Answer 2

Here's a version which just tests for the existence of the encoding file and is therefore independent of the TL version etc. (I assume this should work with e.g. MiKTeX etc. as well. It would also work if you installed a local version of the encoding although I am by no means suggesting that doing so would be wise.)

\documentclass[a4paper,greek,british]{article}% or american note that the LAST specified language is default

\IfFileExists{lgrxenc.def}{%
  \typeout{TexLive version is smaller than 2014, using LGRx} % probably better to change this to a more accurate message e.g. 'lgrxenc.def not found...'
  \usepackage[LGRx,T1]{fontenc}%
}{%
  \typeout{TexLive version is >= 2014, NOT using LGRx}%
  \usepackage[T1]{fontenc}%
}

% \usepackage{xgreek}
\usepackage[utf8]{inputenc}
\usepackage{babel}

\begin{document}

  The starting verse of the Iliad is
  \begin{quotation}\greektext
    Μῆνιν ἄειδε, θεά, Πηληιάδεω Ἀχιλῆος
  \end{quotation}
  and it's really great.

\end{document}

For TL 2014, for example, I get

TexLive version is >= 2014, NOT using LGRx

Answer 3

Quick and dirty test -- without lua, running with pdflatex and lualatex (but not needed in this case) ;-)

\documentclass{article}

\usepackage{xstring}

\IfSubStr{\pdftexbanner}{2014}{%
  \usepackage[T1]{fontenc}%
  \usepackage[greek,english]{babel}
}{%
  \usepackage[LGRx,T1]{fontenc}
}

\usepackage{blindtext}
\begin{document}
\blindtext
\end{document}