lstinputlisting environment in equation- and math environment?

Question

I am trying to semi-automatically import multiple parameters/variables from an excel (via .txt) file into both equation environments and $$ = math environments in (share)latex.

It is semi-automattically because I still need to manually import a .txt file into (share)latex.

My approach consists of the following e.g. test.txt file:

2: The old conversion coefficient k_{roe,Sv}
9.329664
4: The new conversion coefficient {K_{roe,Sv}}_{new}
0
6: r_{worst}
817278.6
8: r_{best}
81727.9

And the numbers are imported with the following/similair latex lines:

\item $K_{sh} = \lstinputlisting[firstline=28,lastline=28]{data_input/test.txt}$

Where the datapoint/number is selected by varying the line number (e.g. 4 to 6) in both firstline=4 and lastline=4.

It works fine in the normal (share)latex environment. However, if I apply the command in a $$ environment, I get the following error:

missing $ inserted

and if I add an extra $ sign after the command e.g.

\item $K_{sh} = \lstinputlisting[firstline=28,lastline=28]{data_input/test.txt}$$

it still get that same error.

So I tried putting it in a math Environment with:

\item $K_{sh} = \ensuremath{\lstinputlisting[firstline=28,lastline=28]{data_input/test.txt}}$

and

\item $K_{sh} = \ensuremath{\lstinputlisting[firstline=28,lastline=28]{data_input/test.txt}}$$

As was suggested in this question. However, the missing $ error still remains.

I fear it might be a double question, but with the searchterms known to me, I have not been able to find a working solution. Would you know the solution?

As to comply with BambOo's tip/comment, I have created the following MWE in which the K_{sh.. lines are tested individually by commenting the other 3 K_{sh.. lines out.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{listings}


\title{MWE import data}
\author{A.T.}
\date{April 2018}

\begin{document}

\maketitle

\section{Introduction}

\ensuremath{test} %Testing whether the \ensuremath command requires a package; it does not.

% $K_{sh} = \lstinputlisting[firstline=2,lastline=2]{test.txt}$

% $K_{sh} = \lstinputlisting[firstline=2,lastline=2]{test.txt}$$

% $K_{sh} = \ensuremath{\lstinputlisting[firstline=2,lastline=2]{test.txt}}$

$K_{sh} = \ensuremath{\lstinputlisting[firstline=2,lastline=2]{test.txt}}$$



\end{document}

It makes use of the following test.txt file in the same folder as main.tex:

2: The old conversion coefficient k_{roe,Sv}
9.329664
4: The new conversion coefficient {K_{roe,Sv}}_{new}
0
6: r_{worst}
817278.6
8: r_{best}
81727.9

I did not find out whether it is convention to post the MWE here as code, or whether to link to an external file, I guess w.r.t. availability reduction when the external source goes off line, code is preferred even though it takes more time to recreate.

Answer 1

I'm not sure listings is the best tool for the job:

\begin{filecontents*}{\jobname.txt}
2: The old conversion coefficient k_{roe,Sv}
9.329664
4: The new conversion coefficient {K_{roe,Sv}}_{new}
0
6: r_{worst}
817278.6
8: r_{best}
81727.9
\end{filecontents*}

\documentclass{article}
\usepackage{datatool,siunitx}

\DTLloaddb[noheader]{data}{\jobname.txt}
\newcommand{\mydatavalue}[1]{%
  \begingroup
  \dtlgetrow{data}{#1}%
  \dtlgetentryfromcurrentrow{\temp}{1}%
  \num{\temp}%
  \endgroup
}

\begin{document}

\begin{itemize}
\item $K_{sh} = \mydatavalue{2}$

\item $K_{sh} = \mydatavalue{4}$

\item $K_{sh} = \mydatavalue{6}$
\end{itemize}

\end{document}

There is possibly a better method with datatool.

A different implementation, as datatool may seem overkill.

\begin{filecontents*}{\jobname.txt}
2: The old conversion coefficient k_{roe,Sv}
9.329664
4: The new conversion coefficient {K_{roe,Sv}}_{new}
0
6: r_{worst}
817278.6
8: r_{best}
81727.9
\end{filecontents*}

\documentclass{article}
\usepackage{xparse,siunitx}

\ExplSyntaxOn

\NewDocumentCommand{\loaddatafile}{O{default}m}
 {% #1 = symbolic name, #2 = file name
  \at_datafile_load:nn { #1 } { #2 }
 }

\NewExpandableDocumentCommand{\getdataline}{O{default}m}
 {
  \seq_item:cn { g_at_datafile_#1_seq } { #2 }
 }

\ior_new:N \g_at_datafile_stream

\cs_new_protected:Nn \at_datafile_load:nn
 {
  \seq_gclear_new:c { g_at_datafile_#1_seq }
  \ior_open:Nn \g_at_datafile_stream { #2 }
  \ior_map_inline:Nn \g_at_datafile_stream
   {
    \seq_put_right:cx { g_at_datafile_#1_seq } { \tl_trim_spaces:n { ##1 } }
   }
  \ior_close:N \g_at_datafile_stream
 }

\ExplSyntaxOff

\loaddatafile{\jobname.txt}

\begin{document}

\begin{itemize}
\item $K_{sh} = \num{\getdataline{2}}$

\item $K_{sh} = \num{\getdataline{4}}$

\item $K_{sh} = \num{\getdataline{6}}$
\end{itemize}

\end{document}

Answer 2

So for future users running into the same problem, here is the implementation of the solution that @egreg gave, (including a script to export your excel parameters to .txt for your convenience):

First add package to main.tex:

\usepackage{datatool,siunitx} %To import data from a textfile

Then

%Make own commands to import variable parameters in main.tex:

\DTLloaddb[noheader]{data0}{data_input/excel_output_L.txt}
\newcommand{\inl}[1]{%
  \begingroup
  \dtlgetrow{data0}{#1}%
  \dtlgetentryfromcurrentrow{\temp}{1}%
  \num{\temp}%
  \endgroup
}

\DTLloaddb[noheader]{data1}{data_input/excel_output_M_G.txt}
\newcommand{\inmg}[1]{%
  \begingroup
  \dtlgetrow{data1}{#1}%
  \dtlgetentryfromcurrentrow{\temp}{1}%
  \num{\temp}%
  \endgroup
}

\DTLloaddb[noheader]{data2}{data_input/excel_output_H.txt}
\newcommand{\inh}[1]{%
  \begingroup
  \dtlgetrow{data2}{#1}%
  \dtlgetentryfromcurrentrow{\temp}{1}%
  \num{\temp}%
  \endgroup
}

After that add txt files to folder: data_input in the (share)latex folder

Proceed by calling the parameters (e.g. the number in line 6 of excel_output_H.txt) with:

\inmg{6}

(Which can be called in a math environment inside a itemize/enumerate environment:

\item $K_{shielding} = \inmg{6}$

And for completeness This is the code that exports the excel columns E3:E100 to .txt for the 3 sheets in "the" workbook:

Sub export_to_txt()
Dim myFile As String, rng As Range, cellValue As Variant, i As Integer, j As Integer
For nr_sheets = 1 To 3
    If nr_sheets = 1 Then
        sheetname = "L"
    End If
    If nr_sheets = 2 Then
        sheetname = "M_G"
    End If
    If nr_sheets = 3 Then
        sheetname = "H"
    End If
    myFile = ThisWorkbook.Path & "\excel_output_" & sheetname & ".txt"
    'MsgBox (sheetname)
    ThisWorkbook.Worksheets(sheetname).Activate
    Set rng = ThisWorkbook.Worksheets(sheetname).Range("E3:E100")
    Open myFile For Output As #1
    For i = 1 To rng.Rows.Count
        For j = 1 To rng.Columns.Count
    cellValue = rng.Cells(i, j).Value
    If j = rng.Columns.Count Then
        Write #1, cellValue
    Else
        Write #1, cellValue,
    End If
        Next j
    Next i
    Close #1
Next nr_sheets
End Sub