Highlight code with squared brackets

Question

I want to show some .ini file in my work. The ini file works with squared brackets. I try to use \lstdefinelanguage but I can't handle it. That is what I try before and in my understanding it should work but it doesn't:

\documentclass{article}

\usepackage{color}
\usepackage{listings}

\lstdefinelanguage{Ini}
{
        tag=[s][],
        tagstyle=\color{blue}\bfseries,
        usekeywordsintag=true
}

\lstset{
    language=Ini
}

\begin{document}

\begin{lstlisting}
[test]
a=15
b=4
[test1]
c=25
d=5
[test2]
e=50
f=5
\end{lstlisting}

\end{document}

That is how it should look:

Highlight the background behind the keywords wouldn't be that necessary but a nice gimmick.

An problem what I don't understand is how should Latex handle this case:

\begin{lstlisting}[language=Ini]
[test]
a=1
\end{lstlisting}

How can latex difference between the property and the content?

Answer 1

The listings documentation (page 44) mentions that the key tag is language specific (to HTML), so you need to make it available to your language

\documentclass{article}
\usepackage{xcolor}
\usepackage{listings}

\lstdefinelanguage{Ini}
{
  basicstyle=\ttfamily\small,
  columns=fullflexible,
  tag=[s]{[]},
  tagstyle=\color{blue}\bfseries,
  usekeywordsintag=true
}[html]

\lstset{
    language=Ini
}

\begin{document}

\begin{lstlisting}
[test]
a=15
b=4
[test1]
c=25
d=5
[test2]
e=50
f=5
\end{lstlisting}

\end{document}

Regarding your last question,"how should LaTeX handle this case"

\begin{lstlisting}[language=Ini]
[test]
a=1
\end{lstlisting}

lstlisting postpones the processing for verbatim material until having read the optional argument for lstlisting.