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I'm using \immediate\write18{./somescript.sh} to execute my own shell script at the beginning of the latex compilation process. Is there a possibility to get the return value afterwards?

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  • 4
    This question has probably been asked before: with \input{|"someCommand --withOptions and arguments"} you can \input from the standard output of someCommand --withOptions and arguments. This also works with \openin. See also this answer that is somehow related.
    – GuM
    Jun 22, 2015 at 17:46
  • Thanks! I searched a bit, but I didn't find anything relevant - maybe because I searched for write18 and not generally shell commands...
    – crateane
    Jun 22, 2015 at 17:50

3 Answers 3

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A very elementary approach using shell facilities:

Write the script execution state (either of the script itself or of the last command to an external file using > redirection and then read this generated file to a \def\foomacro.

\documentclass{book}

\newread\myscriptresult

\begin{document}
\immediate\write18{./myscript.sh; echo $? > scriptresult.txt}
\immediate\openin\myscriptresult=scriptresult.txt
\read\myscriptresult to \ScriptResult
\immediate\closein\myscriptresult

The result was \ScriptResult

\end{document}

myscript.sh:

#!/bin/bash

ls -la
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  • It works really nice, but only when use a filename with an extension, e.g. result.txt. Without this file extension, the latex compilation process stops, as nothing is read into \ScriptResult and a comparison for an \ifnum fails. I don't know, if the file extension is somehow mandatory, or I do something wrong... EDIT: probably it's related to me using luatex, and luatex automatically puts a .tex behind an extension-less filename, like described here: tex.stackexchange.com/a/128326/44467
    – crateane
    Jun 23, 2015 at 15:53
  • @Faekynn: Please don't edit answers. A comment would have been enough and I would have looked.
    – user31729
    Jun 23, 2015 at 19:54
  • OK! I'll keep that in mind :)
    – crateane
    Jun 23, 2015 at 21:15
12

The following MWE show how you can directly \input from, say, the date command. It also shows how to \read the output of date in a control sequence, by means of \openin.

\documentclass[a4paper]{article}
\usepackage[T1]{fontenc}

\newread\teststream
\newcommand*\testline{}
\openin\teststream=|date
\ifeof\teststream
    \typeout{Unable to open test stream.}
\else
    \typeout{Test stream opened.}
    \read\teststream to \testline
    \typeout{\testline}
\fi

\begin{document}
\input{|date}
\end{document}

However, to avoid problems with special characters, it is probably better to use \readline innstead of \read, if you are running with e-TeX extensions enabled (as you ordinarily do, nowadays).

Of course, the above code requires that you enable the shell-escape feature.

Addition

I think it may be useful to add references to a couple of related (questions and) answers: first of all (and above all) there is Write18: capturing shell (script) output as command/variable?; however, none of the answers to this question (or to this other, related one) mention the fact that the “piped input” feature also works with \openin. For this reason, I take the liberty to cite also Include/input every subfile from a subfolder, even if it includes an answer by myself (and this surely qualifies as self-promotion, which isn’t very nice -- please be forgiving).

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  • This solution is nice, but unfortunately not suitable for me: I do want to read the output on the console, and with the other solution I simply added an echo before each exit to my script...
    – crateane
    Jun 22, 2015 at 18:29
  • The advantage of this solution is the testing if the stream exists. Nice solution!
    – user31729
    Jun 22, 2015 at 18:31
1

You can try to use my iexec package, which checks the exit code automatically. If it's not equal to zero, the compilation will stop with an error:

\documentclass{book}
\usepackage{iexec}
\begin{document}
\iexec{./my-script.sh}
\end{document}

The output of ./my-script.sh will automatically be included into the document. This can be disabled with quiet option:

\iexec[quiet]{./my-script.sh}

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