/usr/share/texlive/texmf-dist/tex/plain/graphics-pln/psfrag.tex is in texlive-plain-extra 2014.20141024-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | % Plain TeX interface to psfrag.
% David Carlisle
\input miniltx
\makeatletter
\ifx\@compatibilitytrue\@undefined
\csname newif\expandafter\endcsname
\csname if@compatibility\endcsname
\fi
\ifx\raisebox\@undefined
\def\raisebox#1#2{{%
\setbox0=\hbox{#2}\def\depth{\dp0}\leavevmode\raise#1\box\z@}}
\fi
\ifx\@@underline\@undefined
\let\@@underline\underline
\def\underline{%
\ifmmode\expandafter\@@underline\else\expandafter\underbar\fi}
\fi
\ifx\sbox\@undefined
\def\sbox#1{\setbox#1\hbox}
\fi
% psfrag loads the core graphics package, but only the extended
% graphicx interface is available from plain TeX so just intercept
% the call and ask for graphicx.
\let\savedRP\RequirePackage
\def\RequirePackage#1{%
\let\RequirePackage\savedRP
\ifx\includegraphics\@undefined
\input graphicx\fi\relax}
\input psfrag.sty
\ifx\pfg@dp\@undefined
\csname newdimen\endcsname\pfg@dp
\csname newdimen\endcsname\pfg@wd
\csname newdimen\endcsname\pfg@dx
\csname newdimen\endcsname\pfg@dy
\fi
\resetatcatcode
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