Ship only the last physical page (or the last two/three physical pages)

Question

My question is related to and in continuation to Compiling only a page range or page selection

I would like to output only the last page (or last two/three pages) without knowing the total number of pages in advance. As in the above referred question, compilation should happen for the entire document with all the counters, page number on footers intact.

Is it possible to say something like \keeppages{-1} (from the accepted answer to the above question - https://tex.stackexchange.com/a/96258/26682) and that should do for the last page? I toyed with pageslts package but I dont see any way to achieve what I want.

Any ideas?

PS: the question is self explanatory ... a MWE is not really needed here.

Answer 1

Here is a modification to Compiling only a page range or page selection that allows you to use negative numbers that counts from the last page. So, for example, you could use

\discardpages{-2,-1}

to remove the last two pages, or

\keeppages{-3,-1}

to only keep the third-to-last and final page. The adaptation relies of lastpage to place a \label{LastPage} on the last page and use the page number in calculations (thanks to refcount).

\documentclass{article}

\usepackage{lipsum,atbegshi,etoolbox}
\usepackage{lastpage,refcount}

\makeatletter
\newcommand{\discardpages}[1]{% \discardpages{<csv list>}
  \xdef\discard@pages{#1}% Store pages to discard
  \AtBeginShipout{% At shipout, decide whether to discard page/not
    \renewcommand*{\do}[1]{% How to handle each page entry in csv list
      \ifnum##1<0
        \ifnum\value{page}=\numexpr\getpagerefnumber{LastPage}+##1+1\relax
          \AtBeginShipoutDiscard% Discard page/not
          \gdef\do####1{}% Do nothing further
        \fi
      \else% ##1 >= 0
        \ifnum\value{page}=##1\relax%
          \AtBeginShipoutDiscard% Discard page/not
          \gdef\do####1{}% Do nothing further
        \fi
      \fi
    }%
    \expandafter\docsvlist\expandafter{\discard@pages}% Process list of pages to discard
  }%
}

\newif\ifkeeppage
\newcommand{\keeppages}[1]{% \keeppages{<csv list>}
  \xdef\keep@pages{#1}% Store pages to keep
  \AtBeginShipout{% At shipout, decide whether to discard page/not
    \keeppagefalse%
    \renewcommand*{\do}[1]{% How to handle each page entry in csv list
      \ifnum##1<0
        \ifnum\value{page}=\numexpr\getpagerefnumber{LastPage}+##1+1\relax
          \keeppagetrue% Page should be kept
          \gdef\do####1{}% Do nothing further
        \fi
      \else% ##1 >= 0
        \ifnum\value{page}=##1\relax%
          \keeppagetrue% Page should be kept
          \gdef\do####1{}% Do nothing further
        \fi
      \fi
    }%
    \expandafter\docsvlist\expandafter{\keep@pages}% Process list of pages to keep
    \ifkeeppage\else\AtBeginShipoutDiscard\fi% Discard page/not
  }%
}
\makeatother

%\discardpages{-2,-1}
\keeppages{-3,-1}% Keep these pages.

\begin{document}

\sloppy\lipsum[1-50]\lipsum[1-50]\lipsum[1-50]\lipsum[1-50]\lipsum[1-50]

\end{document}

The LastPage reference will have to settle in order to be effective. So, you'll have to compile at least twice with every change in this \label location (or at the first go).

No further testing was done to see whether atveryend might be required.

Answer 2

The problem with this approach is that TeX's model is built sequentially out of "boxes" and "glue." To figure out what's on the 17th page, the TeX system needs to layout the previous 16 pages. The question you linked defines some macros that remove pages after pdf generation, but those pages are still generated.

The simplest manual way is to open your generated pdf in a viewer and use the "Print to PDF" option, specifying a page range. If you want to do this in an automated way, that would be more platform-dependent.