iniparser 3.1
iniparser documentation


iniParser is a simple C library offering ini file parsing services. The library is pretty small (less than 1500 lines of C) and robust, and does not depend on any other external library to compile. It is written in ANSI C and should compile on most platforms without difficulty.

What is an ini file?

An ini file is an ASCII file describing simple parameters (character strings, integers, floating-point values or booleans) in an explicit format, easy to use and modify for users.

An ini file is segmented into Sections, declared by the following syntax:

    [Section Name]

i.e. the section name enclosed in square brackets, alone on a line. Sections names are allowed to contain any character but square brackets or linefeeds.

In any section are zero or more variables, declared with the following syntax:

    Key = value ; comment

The key is any string (possibly containing blanks). The value is any character on the right side of the equal sign. Values can be given enclosed with quotes. If no quotes are present, the value is understood as containing all characters between the first and the last non-blank characters before the comment. The following declarations are identical:

    Hello = "this is a long string value" ; comment
    Hello = this is a long string value ; comment

The semicolon and comment at the end of the line are optional. If there is a comment, it starts from the first character after the semicolon up to the end of the line.

Multi-line values can be provided by ending the line with a backslash (\).

    Multiple = Line 1 \
    Line 2 \
    Line 3 \
    Line 4 ; comment

This would yield: "multiple" <- "Line1 Line2 Line3 Line4"

Comments in an ini file are:

Compiling/installing the library

Edit the Makefile to indicate the C compiler you want to use, the options to provide to compile ANSI C, and possibly the options to pass to the ar program on your machine to build a library (.a) from a set of object (.o) files.

Defaults are set for the gcc compiler and the standard ar library builder.

Type 'make', that should do it.

To use the library in your programs, add the following line on top of your module:

    #include "iniparser.h"

And link your program with the iniparser library by adding -liniparser.a to the compile line.

See the file test/initest.c for an example.

iniparser is an ANSI C library. If you want to compile it with a C++ compiler you will likely run into compatibility issues. Headers probably have to include the extern "C" hack and function prototypes will want to add some const here and there to keep the compiler happy. This job is left to the reader as there are too many C++ compilers around, each with its own requirements as to what represents acceptable C code in a C++ environment. You have been warned.

Library reference

The library is completely documented in its header file. On-line documentation has been generated and can be consulted here:

Using the parser

Comments are discarded by the parser. Then sections are identified, and in each section a new entry is created for every keyword found. The keywords are stored with the following syntax:

    Keyword = value ; comment

is converted to the following key pair:

    ("section:keyword", "value")

This means that if you want to retrieve the value that was stored in the section called Pizza, in the keyword Cheese, you would make a request to the dictionary for "pizza:cheese". All section and keyword names are converted to lowercase before storage in the structure. The value side is conserved as it has been parsed, though.

Section names are also stored in the structure. They are stored using as key the section name, and a NULL associated value. They can be queried through iniparser_find_entry().

To launch the parser, use the function called iniparser_load(), which takes an input file name and returns a newly allocated dictionary structure. This latter object should remain opaque to the user and only accessed through the following accessor functions:

Finally, discard this structure using iniparser_freedict().

All values parsed from the ini file are stored as strings. The accessors are just converting these strings to the requested type on the fly, but you could basically perform this conversion by yourself after having called the string accessor.

Notice that iniparser_getboolean() will return an integer (0 or 1), trying to make sense of what was found in the file. Strings starting with "y", "Y", "t", "T" or "1" are considered true values (return 1), strings starting with "n", "N", "f", "F", "0" are considered false (return 0). This allows some flexibility in handling of boolean answers.

If you want to add extra information into the structure that was not present in the ini file, you can use iniparser_set() to insert a string.

If you want to add a section to the structure, add a key with a NULL value. Example:

    iniparser_set(ini, "section", NULL);
    iniparser_set(ini, "section:key1", NULL);
    iniparser_set(ini, "section:key2", NULL);

A word about the implementation

The dictionary structure is a pretty simple dictionary implementation which might find some uses in other applications. If you are curious, look into the source.

Known defects

The dictionary structure is extremely unefficient for searching as keys are sorted in the same order as they are read from the ini file, which is convenient when dumping back to a file. The simplistic first-approach linear search implemented there can become a bottleneck if you have a very large number of keys.

People who need to load large amounts of data from an ini file should definitely turn to more appropriate solutions: sqlite3 or similar. There are otherwise many other dictionary implementations available on the net to replace this one.


Nicolas Devillard (ndevilla AT free DOT fr).