inih (INI Not Invented Here)

inih (INI Not Invented Here) is a simple .INI file parser written in C. It's only a couple of pages of code, and it was designed to be small and simple, so it's good for embedded systems. It's also more or less compatible with Python's ConfigParser style of .INI files, including RFC 822-style multi-line syntax and name: value entries.

To use it, just give ini_parse() an INI file, and it will call a callback for every name=value pair parsed, giving you strings for the section, name, and value. It's done this way ("SAX style") because it works well on low-memory embedded systems, but also because it makes for a KISS implementation.

You can also call ini_parse_file() to parse directly from a FILE* object, ini_parse_string() to parse data from a string, or ini_parse_stream() to parse using a custom fgets-style reader function for custom I/O.

Download a release, browse the source, or read about how to use inih in a DRY style with X-Macros.

Compile-time options

You can control various aspects of inih using preprocessor defines:

Syntax options

• Multi-line entries: By default, inih supports multi-line entries in the style of Python's ConfigParser. To disable, add -DINI_ALLOW_MULTILINE=0.
• UTF-8 BOM: By default, inih allows a UTF-8 BOM sequence (0xEF 0xBB 0xBF) at the start of INI files. To disable, add -DINI_ALLOW_BOM=0.
• Inline comments: By default, inih allows inline comments with the ; character. To disable, add -DINI_ALLOW_INLINE_COMMENTS=0. You can also specify which character(s) start an inline comment using INI_INLINE_COMMENT_PREFIXES.
• Start-of-line comments: By default, inih allows both ; and # to start a comment at the beginning of a line. You can override this by changing INI_START_COMMENT_PREFIXES.

Parsing options

• Stop on first error: By default, inih keeps parsing the rest of the file after an error. To stop parsing on the first error, add -DINI_STOP_ON_FIRST_ERROR=1.
• Report line numbers: By default, the ini_handler callback doesn't receive the line number as a parameter. If you need that, add -DINI_HANDLER_LINENO=1.
• Call handler on new section: By default, inih only calls the handler on each name=value pair. To detect new sections (e.g., the INI file has multiple sections with the same name), add -DINI_CALL_HANDLER_ON_NEW_SECTION=1. Your handler function will then be called each time a new section is encountered, with section set to the new section name but name and value set to NULL.

Memory options

• Stack vs heap: By default, inih creates a fixed-sized line buffer on the stack. To allocate on the heap using malloc instead, specify -DINI_USE_STACK=0.
• Maximum line length: The default maximum line length (for stack or heap) is 200 bytes. To override this, add something like -DINI_MAX_LINE=1000. Note that INI_MAX_LINE must be 3 more than the longest line (due to \r, \n, and the NUL).
• Allow realloc: By default when using the heap (-DINI_USE_STACK=0), inih allocates a fixed-sized buffer of INI_INITIAL_ALLOC bytes. To allow this to grow to INI_MAX_LINE bytes, doubling if needed, set -DINI_ALLOW_REALLOC=1.
• Initial malloc size: INI_INITIAL_ALLOC specifies the initial malloc size when using the heap. It defaults to 200 bytes.

Simple example in C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "../ini.h"

typedef struct
{
    int version;
    const char* name;
    const char* email;
} configuration;

static int handler(void* user, const char* section, const char* name,
                   const char* value)
{
    configuration* pconfig = (configuration*)user;

    #define MATCH(s, n) strcmp(section, s) == 0 && strcmp(name, n) == 0
    if (MATCH("protocol", "version")) {
        pconfig->version = atoi(value);
    } else if (MATCH("user", "name")) {
        pconfig->name = strdup(value);
    } else if (MATCH("user", "email")) {
        pconfig->email = strdup(value);
    } else {
        return 0;  /* unknown section/name, error */
    }
    return 1;
}

int main(int argc, char* argv[])
{
    configuration config;

    if (ini_parse("test.ini", handler, &config) < 0) {
        printf("Can't load 'test.ini'\n");
        return 1;
    }
    printf("Config loaded from 'test.ini': version=%d, name=%s, email=%s\n",
        config.version, config.name, config.email);
    return 0;
}

C++ example

If you're into C++ and the STL, there is also an easy-to-use INIReader class that stores values in a map and lets you Get() them:

#include <iostream>
#include "INIReader.h"

int main()
{
    INIReader reader("../examples/test.ini");

    if (reader.ParseError() < 0) {
        std::cout << "Can't load 'test.ini'\n";
        return 1;
    }
    std::cout << "Config loaded from 'test.ini': version="
              << reader.GetInteger("protocol", "version", -1) << ", name="
              << reader.Get("user", "name", "UNKNOWN") << ", email="
              << reader.Get("user", "email", "UNKNOWN") << ", pi="
              << reader.GetReal("user", "pi", -1) << ", active="
              << reader.GetBoolean("user", "active", true) << "\n";
    return 0;
}

This simple C++ API works fine, but it's not very fully-fledged. I'm not planning to work more on the C++ API at the moment, so if you want a bit more power (for example GetSections() and GetFields() functions), see these forks:

• https://github.com/Blandinium/inih
• https://github.com/OSSystems/inih

Differences from ConfigParser

Some differences between inih and Python's ConfigParser standard library module:

• INI name=value pairs given above any section headers are treated as valid items with no section (section name is an empty string). In ConfigParser having no section is an error.
• Line continuations are handled with leading whitespace on continued lines (like ConfigParser). However, instead of concatenating continued lines together, they are treated as separate values for the same key (unlike ConfigParser).

Platform-specific notes

• Windows/Win32 uses UTF-16 filenames natively, so to handle Unicode paths you need to call _wfopen() to open a file and then ini_parse_file() to parse it; inih does not include wchar_t or Unicode handling.

Related links

• Conan package for inih (Conan is a C/C++ package manager)