Intro To 'ptx' Command In Linux

2023-10-11 - By Robert Elder

I use the 'ptx' command to produce the permuted index of a text document:

ptx story.txt

                                       Once upon a time.
                           Once upon   a time.
                         Once upon a   time.
                                Once   upon a time.

What Does The 'ptx' Command Do?

A permuted index, also known as a 'key word in context', is part of an obsolete method of organizing keywords in a piece of documentation.

The 'ptx' command first appeared in 1972 as a user maintained program, in the second edition of the Unix programmers manual:

This manual states that "The index for this manual was generated using ptx.":

Source: Unix Programmer's Manual, Second Edition 1972.

Example Use Case Of 'ptx' Command

Here, I have a text document in the file 'instructions.txt' that contains some instructions:

Maximum operating efficiency of a cat is achieve by petting it in slow motion.

This ptx command:

ptx instructions.txt

will produce a permuted index of all words in the document as follows:

   cat is achieve by petting/          Maximum operating efficiency of a
     Maximum operating efficiency of   a cat is achieve by petting it in/
             /efficiency of a cat is   achieve by petting it in slow/
     /efficiency of a cat is achieve   by petting it in slow motion.
          /operating efficiency of a   cat is achieve by petting it in/
   petting it/     Maximum operating   efficiency of a cat is achieve by
      a cat is achieve by petting it   in slow motion.       /efficiency of
      /operating efficiency of a cat   is achieve by petting it in slow/
      of a cat is achieve by petting   it in slow motion.       /efficiency
       achieve by petting it in slow   motion.                 /of a cat is
        Maximum operating efficiency   of a cat is achieve by petting it/
   achieve by petting/       Maximum   operating efficiency of a cat is
             /of a cat is achieve by   petting it in slow motion.
     cat is achieve by petting it in   slow motion.                   /of a

Notice these words are sorted in the above output:

   ... .. ....... .. ........          Maximum ......... .......... .. .
     ....... ......... .......... ..   a ... .. ....... .. ....... .. ...
             ........... .. . ... ..   achieve .. ....... .. .. .....
     ........... .. . ... .. .......   by ....... .. .. .... .......
          .......... .......... .. .   cat .. ....... .. ....... .. ...
   ....... ...     ....... .........   efficiency .. . ... .. ....... ..
      . ... .. ....... .. ....... ..   in .... .......       ........... ..
      .......... .......... .. . ...   is ....... .. ....... .. .. .....
      .. . ... .. ....... .. .......   it .. .... .......       ...........
       ....... .. ....... .. .. ....   motion.                 ... . ... ..
        ....... ......... ..........   of . ... .. ....... .. ....... ...
   ....... .. ........       .......   operating .......... .. . ... ..
             ... . ... .. ....... ..   petting .. .. .... .......
     ... .. ....... .. ....... .. ..   slow .......                   ... .

I can specify an ignore file called 'ignore.txt' to ingore common English words:

a
by
in
is
it
of

Now, if I re-run the 'ptx' command and specify the ignore file, the output will be less verbose and omit lines that center on the ignored keywords:

ptx --ignore-file=ignore.txt instructions.txt

   cat is achieve by petting/          Maximum operating efficiency of a
             /efficiency of a cat is   achieve by petting it in slow/
          /operating efficiency of a   cat is achieve by petting it in/
   petting it/     Maximum operating   efficiency of a cat is achieve by
       achieve by petting it in slow   motion.                 /of a cat is
   achieve by petting/       Maximum   operating efficiency of a cat is
             /of a cat is achieve by   petting it in slow motion.
     cat is achieve by petting it in   slow motion.                   /of a

Creating PDF Documentation Using 'ptx' Command Output

I can use the '--format' flag to format the permuted index into a typesetting language like tex for further processing:

ptx --ignore-file=ignore.txt --format=tex instructions.txt

And the output will look something like this:

\xx {cat is achieve by petting}{}{Maximum}{ operating efficiency of a}{}
\xx {}{efficiency of a cat is}{achieve}{ by petting it in slow}{}
\xx {}{operating efficiency of a}{cat}{ is achieve by petting it in}{}
\xx {petting it}{Maximum operating}{efficiency}{ of a cat is achieve by}{}
\xx {}{achieve by petting it in slow}{motion}{.}{of a cat is}
\xx {achieve by petting}{Maximum}{operating}{ efficiency of a cat is}{}
\xx {}{of a cat is achieve by}{petting}{ it in slow motion.}{}
\xx {}{cat is achieve by petting it in}{slow}{ motion.}{of a}

I can take the above output and surround it with these latex directives to produce a finished .tex document:

cat << EOF >> indx.tex
\documentclass{article}
\usepackage{adjustbox}
\begin{document}
\newcommand{\xx}[5]{{#1} & {#2} & \textbf{{#3}} & {#4} & {#5} \\\\}
\noindent\sffamily
\begin{adjustbox}{center}
\begin{tabular}{lrllr}
 & & \textbf{The Key Word} & & \\\\
\hline
EOF

ptx --ignore-file=ignore.txt --format=tex instructions.txt >> indx.tex

cat << EOF >> indx.tex
\end{tabular}
\end{adjustbox}
\end{document}
EOF

And the final '*.tex' document will look like this:

\documentclass{article}
\usepackage{adjustbox}
\begin{document}
\newcommand{\xx}[5]{{#1} & {#2} & \textbf{{#3}} & {#4} & {#5} \\}
\noindent\sffamily
\begin{adjustbox}{center}
\begin{tabular}{lrllr}
 & & \textbf{The Key Word} & & \\
\hline
\xx {cat is achieve by petting}{}{Maximum}{ operating efficiency of a}{}
\xx {}{efficiency of a cat is}{achieve}{ by petting it in slow}{}
\xx {}{operating efficiency of a}{cat}{ is achieve by petting it in}{}
\xx {petting it}{Maximum operating}{efficiency}{ of a cat is achieve by}{}
\xx {}{achieve by petting it in slow}{motion}{.}{of a cat is}
\xx {achieve by petting}{Maximum}{operating}{ efficiency of a cat is}{}
\xx {}{of a cat is achieve by}{petting}{ it in slow motion.}{}
\xx {}{cat is achieve by petting it in}{slow}{ motion.}{of a}
\end{tabular}
\end{adjustbox}
\end{document}

This '*.tex' document can be compiled into a '*.dvi' file using this command:

latex indx.tex

The resulting '*.dvi' file can be compiled into a '*.ps' file using this command:

dvips indx.dvi

And finally, the resulting '*.ps' file can be compiled into a PDF document using this command:

ps2pdf indx.ps

You can view the final completed permutation index pdf document here.

And that's why the 'ptx' command is my favourite Linux command.

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