如何扩展文件内容以附加和计算行数？

Question

计算行数filecontents很容易，因为环境会逐行处理其内容，读取、检查环境是否结束，然后写入。您只需创建一个计数器，并在每次写入一行时添加它即可。

追加比较棘手。首先，TeX（至少没有 Lua）无法打开具有“追加”权限的文件，因此这被排除在外。让文件保持打开状态，然后稍后恢复写入的想法乍一看似乎更容易，但您需要跨环境保存一堆变量，然后您将无法写入文件a，然后b，然后追加到a。

在下面的代码中，\filecontents@preappend宏（append使用选项时）将参数中的文件读取到临时宏中，然后将\filecontents@append读取的宏放入输入流中，然后放入环境的实际内容之前，因此它就像您一次性输入所有内容一样工作。选项append隐含overwrite和noheader选项。

为了紧凑起见，我试图将代码写成补丁，但显然修补命令会丢失^^J字符，然后标题会折叠为一行，因此这是对的完全重新定义\filec@ntents，但更改的行已标记。

\documentclass{article}
\usepackage{expl3}
\ExplSyntaxOn
\cs_new_eq:NN \FileSize \file_size:n
\ExplSyntaxOff
\makeatletter
\begingroup%
\@tempcnta=1
\loop
  \catcode\@tempcnta=12  %
  \advance\@tempcnta\@ne %
\ifnum\@tempcnta<32      %
\repeat                  %
\catcode`\^^M\active
\catcode`\^^L\active\let^^L\relax
\catcode`\^^I\active
\gdef\filec@ntents#1{%
  \set@curr@file{\filec@ntents@checkdir#1}%
  \edef\q@curr@file{\expandafter\quote@name\expandafter{\@curr@file}}%
  \filecontents@preappend% <- ADDED for appending
  \gaborit@reset@counter% <- ADDED for counting lines
  \gaborit@reset@append% <- ADDED for counting lines
  \openin\@inputcheck\q@curr@file \space %
  \ifeof\@inputcheck%
    \@latex@warning@no@line%
        {Writing file `\@currdir\@curr@file'}%
    \chardef\reserved@c15 %
    \ch@ck7\reserved@c\write%
    \immediate\openout\reserved@c\q@curr@file\relax%
  \else%
    \if@filesw%
      \@latex@warning@no@line%
          {File `\@curr@file' already \filec@ntents@where.\MessageBreak%
             Not generating it from this source}%
      \let\gaborit@step@counter\@empty% <- ADDED for counting lines
      \let\gaborit@count@header\@empty% <- ADDED for counting lines
      \let\write\@gobbletwo%
      \let\closeout\@gobble%
    \else%
      \edef\reserved@a{#1}%
      \edef\reserved@a{\detokenize\expandafter{\reserved@a}}%
      \edef\reserved@b{\detokenize\expandafter{\jobname}}%
      \ifx\reserved@a\reserved@b%
        \@fileswtrue%
      \else%
        \edef\reserved@b{\reserved@b\detokenize{.tex}}%
        \ifx\reserved@a\reserved@b
          \@fileswtrue%
        \fi%
      \fi%
      \chardef\reserved@c15 %
      \ch@ck7\reserved@c\write%
      \if@filesw%  % Foul ... trying to overwrite \jobname!
      \@latex@error{Trying to overwrite `\jobname.tex'}{You can't %
        write to the file you a reading from!\MessageBreak%
        Data is written to screen instead.}%
      \else%
        \@latex@warning@no@line%
           {Writing or overwriting file `\@currdir\@curr@file'}%
        \immediate\openout\reserved@c#1\relax%
      \fi%
    \fi%
  \fi%
  \closein\@inputcheck%
  \if@tempswa%
    \gaborit@count@header% <- ADDED for counting lines
    \immediate\write\reserved@c{%
      \@percentchar\@percentchar\space%
          \expandafter\@gobble\string\LaTeX2e file `\@curr@file'^^J%
      \@percentchar\@percentchar\space  generated by the %
        `\@currenvir' \expandafter\@gobblefour\string\newenvironment^^J%
      \@percentchar\@percentchar\space from source `\jobname' on %
         \number\year/\two@digits\month/\two@digits\day.^^J%
      \@percentchar\@percentchar}%
  \fi%
  \let\do\@makeother\dospecials%
  \count@ 128\relax%
  \loop%
    \catcode\count@ 11\relax%
    \advance\count@ \@ne%
    \ifnum\count@<\@cclvi%
  \repeat%
  \edef\E{\@backslashchar end\string{\@currenvir\string}}%
  \edef\reserved@b{%
    \def\noexpand\reserved@b%
         ####1\E####2\E####3\relax}%
  \reserved@b{%
    \ifx\gaborit@reset@append##1\relax% <- ADDED for counting lines
      \gaborit@reset@append% <- ADDED for counting lines
    \else% <- ADDED for counting lines
    \ifx\relax##3\relax%
      \immediate\write\reserved@c{##1}%
      \gaborit@step@counter% <- ADDED for counting lines
    \else%
      \edef^^M{\noexpand\end{\@currenvir}}%
      \ifx\relax##1\relax%
      \else%
          \@latex@warning{Writing text `##1' before %
             \string\end{\@currenvir}\MessageBreak as last line of \@curr@file}%
        \immediate\write\reserved@c{##1}%
        \gaborit@step@counter% <- ADDED for counting lines
      \fi%
      \ifx\relax##2\relax%
      \else%
         \@latex@warning{%
           Ignoring text `##2' after \string\end{\@currenvir}}%
      \fi%
    \fi%
    \fi% <- ADDED for counting lines
    ^^M}%
  \catcode`\^^L\active%
  \let\L\@undefined%
  \def^^L{\expandafter\ifx\csname L\endcsname\relax\fi ^^J^^J}%
  \catcode`\^^I\active%
  \let\I\@undefined%
  \def^^I{\expandafter\ifx\csname I\endcsname\relax\fi\space}%
  \catcode`\^^M\active%
  \edef^^M##1^^M{%
    \noexpand\reserved@b##1\E\E\relax}%
  \filecontents@append}% <- ADDED for appending
%
% Code for append
\gdef\gaborit@pre@append{%
  \begingroup%
    \catcode`\^^L\active%
    \catcode`\^^I\active%
    \catcode`\^^M\active%
    \let\do\@makeother\dospecials%
    \count@ 128\relax%
    \loop%
      \catcode\count@ 11\relax%
      \advance\count@ \@ne%
      \ifnum\count@<\@cclvi%
    \repeat%
    \let^^M\relax%
    \edef\gaborit@tmpa{\FileSize{\q@curr@file}}%
    \ifnum\expandafter\@car\gaborit@tmpa\@nil=0\relax%
      \endgroup \def\gaborit@append{^^M\gaborit@reset@append}%
    \else%
      \everyeof{\noexpand}%
      \edef\gaborit@tmpa{\@@input\q@curr@file \space}%
      \edef\x{\endgroup%
        \edef\noexpand\gaborit@append{%
          \noexpand\gaborit@trim@EOF\gaborit@tmpa\noexpand\gaborit@EOF}}\x%
    \fi%
  \filec@ntents@overwrite%
  \filec@ntents@noheader}%
\gdef\gaborit@trim@EOF#1^^M\gaborit@EOF{^^M#1%
  ^^M\noexpand\gaborit@reset@append}%
\endgroup%
\def\filec@ntents@append{%
  \let\filecontents@preappend\gaborit@pre@append
  \def\filecontents@append{\gaborit@append}}
\let\filecontents@preappend\@empty
\let\filecontents@append\@empty
%
% For counting lines
\newcounter{FC@total@lines}
\newcounter{FC@lines}
\def\gaborit@reset@counter{\setcounter{FC@total@lines}{0}}
\def\gaborit@reset@append{\setcounter{FC@lines}{0}}
\def\gaborit@step@counter{%
  \stepcounter{FC@total@lines}%
  \stepcounter{FC@lines}}
\def\gaborit@count@header{%
  \addtocounter{FC@total@lines}{4}%
  \addtocounter{FC@lines}{4}} % Number of lines in the header
\makeatother

\begin{filecontents}[overwrite]{testfile.tex}
a
b
c
\end{filecontents}
\typeout{\arabic{FC@total@lines} lines written; \arabic{FC@lines} appended}

\begin{filecontents}[append]{testfile.tex}
d
e
f
g
\end{filecontents}
\typeout{\arabic{FC@total@lines} lines written; \arabic{FC@lines} appended}

\begin{document}
\end{document}

运行此代码，TeX 会打印到终端：

LaTeX Warning: Writing or overwriting file `./testfile.tex'.

7 lines written; 7 appended
(./testfile.tex)

LaTeX Warning: Writing or overwriting file `./testfile.tex'.

11 lines written; 4 appended

（FC@total@lines保存文件中的总行数，计数器FC@lines仅保存附加的行数）并且文件testfile.tex包含：

%% LaTeX2e file `testfile.tex'
%% generated by the `filecontents' environment
%% from source `test' on 2019/12/20.
%%
a
b
c
d
e
f
g

正如您指出的，当您这样做时：

\begin{filecontents*}{testfile.tex}
\end{filecontents*}
%
\begin{filecontents}[append]{testfile.tex}
a
\end{filecontents}

（即什么都不写，然后在后面附加一行a）您得到的文件是：

这是因为当 TeX 读取一个空文件时，它会将该文件视为一个只有一个空行¹的文件，因此您无法轻易区分这两种情况，而必须选择较小的危害：要么在附加到空文件时在文件开头出现一个虚假的空行，要么在写入包含单个空行的文件时删除一个空行。

但是，使用 pdfTeX 中引入的文件实用程序（但现在其他引擎中也可用），您可以查询文件的大小（以字节为单位），因此对于空文件，您可以采取不同的行为。在代码中，我使用了expl3's\file_size:n来避免处理不存在的文件。

^1.您可以通过此测试文件看到这一点：

\catcode`\@=11
\newwrite\test
\def\testit#1{\immediate\openout\test \jobname.testfile\relax #1%
  {\catcode`\^^M=13 \everyeof{\noexpand}%
   \edef\tmpa{\ifdefined\@@input \@@input \else \input \fi \jobname.testfile }\show\tmpa}%
  \immediate\closeout\test}%
\testit{}% empty file
\testit{\immediate\write\test{}}% single empty line
\csname stop\endcsname\bye

我认为，这种行为是由于 TeX\endlinechar在每行末尾添加造成的。当它读取一个空文件时，它仍然会读取一行（即使是空的），然后插入 ( \endlinechar) ^^M，这使得文件看起来好像只有一行空。

Answer 1