How to Extract Line Numbers for INI File Options Using C Libraries?

Finding Line Numbers of Ini File Options Using C Libraries

Problem:

Developers often need to find line numbers where specific options or sections are found in an INI file. This information can pinpoint errors or assist in managing configuration.

C Libraries for INI File Parsing:

• boost::program_options: This library provides parsing for INI-style configuration files but does not offer line number reporting.
• Boost Spirit (Custom Solution): Boost Spirit is an elegant C parser framework that can be tailored to parse INI files and extract line numbers.

Custom Solution with Boost Spirit:

The custom solution presented here uses Boost Spirit's parser framework and provides full line number information.

Example Code:

<code class="cpp">#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/support_line_pos_iterator.hpp>
#include <map>
#include <string>

namespace qi = boost::spirit::qi;

struct textnode_t
{
    int sline, eline, scol, ecol;
    std::string text;
};

// Define INI parser grammar
qi::rule<boost::spirit::line_pos_iterator<std::string::const_iterator>, std::map<textnode_t, textnode_t>()> inifile;</code>

In this code, textnode_t stores line number and column information, while inifile defines the grammar for parsing INI files.

Usage:

Load the INI file into a std::string named input and iterate through the parsed map:

<code class="cpp">boost::spirit::line_pos_iterator<std::string::const_iterator> f(input.begin()), l(input.end());
std::map<textnode_t, textnode_t> data;
qi::phrase_parse(f, l, inifile, qi::space, data);

for (const auto& [k, v] : data)
{
    std::cout << "Key: " << k.text << ", Line: " << k.sline << "\n"
              << "Value: " << v.text << ", Line: " << v.sline << "\n\n";
}</code>

Advantages of Custom Solution:

• Full line number information for both keys and values
• Ability to handle comments and whitespace
• Flexibility to customize parsing behavior as needed

Conclusion:

By utilizing Boost Spirit, you can parse INI files and retrieve line numbers with precision. This functionality is crucial for validating configuration files and resolving configuration issues.

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