path: root/doc/libconfig.info

This is libconfig.info, produced by makeinfo version 4.13 from
libconfig.texi.

INFO-DIR-SECTION Software libraries
START-INFO-DIR-ENTRY
* libconfig: (libconfig).       A Library For Processing Structured Configuration Files
END-INFO-DIR-ENTRY


File: libconfig.info,  Node: Top,  Next: Introduction,  Up: (dir)

libconfig
*********

* Menu:

* Introduction::
* Configuration Files::
* The C API::
* The C++ API::
* Example Programs::
* Configuration File Grammar::
* License::
* Function Index::
* Type Index::
* Concept Index::


File: libconfig.info,  Node: Introduction,  Next: Configuration Files,  Prev: Top,  Up: Top

* Menu:

* Why Another Configuration File Library?::
* Using the Library from a C Program::
* Using the Library from a C++ Program::
* Multithreading Issues::
* Internationalization Issues::
* Compiling Using pkg-config::
* Version Test Macros::

1 Introduction
**************

Libconfig is a library for reading, manipulating, and writing
structured configuration files. The library features a fully reentrant
parser and includes bindings for both the C and C++ programming
languages.

   The library runs on modern POSIX-compilant systems, such as Linux,
Solaris, and Mac OS X (Darwin), as well as on Microsoft Windows 2000/XP
and later (with either Microsoft Visual Studio 2005 or later, or the
GNU toolchain via the MinGW environment).


File: libconfig.info,  Node: Why Another Configuration File Library?,  Next: Using the Library from a C Program,  Up: Introduction

1.1 Why Another Configuration File Library?
===========================================

There are several open-source configuration file libraries available as
of this writing. This library was written because each of those
libraries falls short in one or more ways. The main features of
libconfig that set it apart from the other libraries are:

   * A fully reentrant parser. Independent configurations can be parsed
     in concurrent threads at the same time.

   * Both C and C++ bindings, as well as hooks to allow for the
     creation of wrappers in other languages.

   * A simple, structured configuration file format that is more
     readable and compact than XML and more flexible than the obsolete
     but prevalent Windows "INI" file format.

   * A low-footprint implementation (just 37K for the C library and 76K
     for the C++ library) that is suitable for memory-constrained
     systems.

   * Proper documentation.



File: libconfig.info,  Node: Using the Library from a C Program,  Next: Using the Library from a C++ Program,  Prev: Why Another Configuration File Library?,  Up: Introduction

1.2 Using the Library from a C Program
======================================

To use the library from C code, include the following preprocessor
directive in your source files:


     #include <libconfig.h>


   To link with the library, specify `-lconfig' as an argument to the
linker.


File: libconfig.info,  Node: Using the Library from a C++ Program,  Next: Multithreading Issues,  Prev: Using the Library from a C Program,  Up: Introduction

1.3 Using the Library from a C++ Program
========================================

To use the library from C++, include the following preprocessor
directive in your source files:


     #include <libconfig.h++>


   Or, alternatively:


     #include <libconfig.hh>


   The C++ API classes are defined in the namespace `libconfig', hence
the following statement may optionally be used:


     using namespace libconfig;


   To link with the library, specify `-lconfig++' as an argument to the
linker.


File: libconfig.info,  Node: Multithreading Issues,  Next: Internationalization Issues,  Prev: Using the Library from a C++ Program,  Up: Introduction

1.4 Multithreading Issues
=========================

Libconfig is fully "reentrant"; the functions in the library do not
make use of global variables and do not maintain state between
successive calls. Therefore two independent configurations may be safely
manipulated concurrently by two distinct threads.

   Libconfig is not "thread-safe". The library is not aware of the
presence of threads and knows nothing about the host system's threading
model. Therefore, if an instance of a configuration is to be accessed
from multiple threads, it must be suitably protected by synchronization
mechanisms like read-write locks or mutexes; the standard rules for
safe multithreaded access to shared data must be observed.

   Libconfig is not "async-safe". Calls should not be made into the
library from signal handlers, because some of the C library routines
that it uses may not be async-safe.

   Libconfig is not guaranteed to be "cancel-safe". Since it is not
aware of the host system's threading model, the library does not
contain any thread cancellation points. In most cases this will not be
an issue for multithreaded programs. However, be aware that some of the
routines in the library (namely those that read/write configurations
from/to files or streams) perform I/O using C library routines which
may potentially block; whether or not these C library routines are
cancel-safe depends on the host system.


File: libconfig.info,  Node: Internationalization Issues,  Next: Compiling Using pkg-config,  Prev: Multithreading Issues,  Up: Introduction

1.5 Internationalization Issues
===============================

Libconfig does not natively support Unicode configuration files, but
string values may contain Unicode text encoded in UTF-8; such strings
will be treated as ordinary 8-bit ASCII text by the library. It is the
responsibility of the calling program to perform the necessary
conversions to/from wide (wchar_t) strings using the wide string
conversion functions such as mbsrtowcs() and wcsrtombs() or the iconv()
function of the libiconv library.

   The textual representation of a floating point value varies by
locale. However, the libconfig grammar specifies that floating point
values are represented using a period (`.') as the radix symbol; this
is consistent with the grammar of most programming languages. When a
configuration is read in or written out, libconfig temporarily changes
the LC_NUMERIC category of the locale of the calling thread to the "C"
locale to ensure consistent handling of floating point values
regardless of the locale(s) in use by the calling program.

   Note that the MinGW environment does not (as of this writing) provide
functions for changing the locale of the calling thread. Therefore,
when using libconfig in that environment, the calling program is
responsible for changing the LC_NUMERIC category of the locale to the
"C" locale before reading or writing a configuration.


File: libconfig.info,  Node: Compiling Using pkg-config,  Next: Version Test Macros,  Prev: Internationalization Issues,  Up: Introduction

1.6 Compiling Using pkg-config
==============================

On UNIX systems you can use the pkg-config utility (version 0.20 or
later) to automatically select the appropriate compiler and linker
switches for libconfig. Ensure that the environment variable
`PKG_CONFIG_PATH' contains the absolute path to the `lib/pkgconfig'
subdirectory of the libconfig installation. Then, you can compile and
link C programs with libconfig as follows:

     gcc `pkg-config --cflags libconfig` myprogram.c -o myprogram \
         `pkg-config --libs libconfig`


   And similarly, for C++ programs:

     g++ `pkg-config --cflags libconfig++` myprogram.cpp -o myprogram \
         `pkg-config --libs libconfig++`


   Note the backticks in the above examples.

   When using autoconf, the `PKG_CHECK_MODULES' m4 macro may be used to
check for the presence of a given version of libconfig, and set the
appropriate Makefile variables automatically. For example:

     PKG_CHECK_MODULES([LIBCONFIGXX], [libconfig++ >= 1.4],,
       AC_MSG_ERROR([libconfig++ 1.4 or newer not found.])
     )

   In the above example, if libconfig++ version 1.4 or newer is found,
the Makefile variables `LIBCONFIGXX_LIBS' and `LIBCONFIGXX_CFLAGS' will
be set to the appropriate compiler and linker flags for compiling with
libconfig, and if it is not found, the configure script will abort with
an error to that effect.


File: libconfig.info,  Node: Version Test Macros,  Prev: Compiling Using pkg-config,  Up: Introduction

1.7 Version Test Macros
=======================

The `libconfig.h' header declares the following macros:

 -- Macro: LIBCONFIG_VER_MAJOR
 -- Macro: LIBCONFIG_VER_MINOR
 -- Macro: LIBCONFIG_VER_REVISION
     These macros represent the major version, minor version, and
     revision of the libconfig library. For example, in libconfig 1.4
     these are defined as `1', `4', and `0', respectively. These macros
     can be used in preprocessor directives to determine which
     libconfig features and/or APIs are present. For example:

          #if (((LIBCONFIG_VER_MAJOR == 1) && (LIBCONFIG_VER_MINOR >= 4)) \
               || (LIBCONFIG_VER_MAJOR > 1))
            /* use features present in libconfig 1.4 and later */
          #endif

     These macros were introduced in libconfig 1.4.


   Similarly, the `libconfig.h++' header declares the following macros:

 -- Macro: LIBCONFIGXX_VER_MAJOR
 -- Macro: LIBCONFIGXX_VER_MINOR
 -- Macro: LIBCONFIGXX_VER_REVISION
     These macros represent the major version, minor version, and
     revision of the libconfig++ library.



File: libconfig.info,  Node: Configuration Files,  Next: The C API,  Prev: Introduction,  Up: Top

* Menu:

* Settings::
* Groups::
* Arrays::
* Lists::
* Integer Values::
* 64-bit Integer Values::
* Floating Point Values::
* Boolean Values::
* String Values::
* Comments::
* Include Directives::

2 Configuration Files
*********************

Libconfig supports structured, hierarchical configurations. These
configurations can be read from and written to files and manipulated in
memory.

   A "configuration" consists of a group of "settings", which associate
names with values. A "value" can be one of the following:

   * A "scalar value": integer, 64-bit integer, floating-point number,
     boolean, or string

   * An "array", which is a sequence of scalar values, all of which
     must have the same type

   * A "group", which is a collection of settings

   * A "list", which is a sequence of values of any type, including
     other lists

   Consider the following configuration file for a hypothetical GUI
application, which illustrates all of the elements of the configuration
file grammar.


     # Example application configuration file

     version = "1.0";

     application:
     {
       window:
       {
         title = "My Application";
         size = { w = 640; h = 480; };
         pos = { x = 350; y = 250; };
       };

       list = ( ( "abc", 123, true ), 1.234, ( /* an empty list */) );

       books = ( { title  = "Treasure Island";
                   author = "Robert Louis Stevenson";
                   price  = 29.95;
                   qty    = 5; },
                 { title  = "Snow Crash";
                   author = "Neal Stephenson";
                   price  = 9.99;
                   qty    = 8; } );

       misc:
       {
         pi = 3.141592654;
         bigint = 9223372036854775807L;
         columns = [ "Last Name", "First Name", "MI" ];
         bitmask = 0x1FC3;
       };
     };


   Settings can be uniquely identified within the configuration by a
"path". The path is a dot-separated sequence of names, beginning at a
top-level group and ending at the setting itself. Each name in the path
is the name of a setting; if the setting has no name because it is an
element in a list or array, an integer index in square brackets can be
used as the name.

   For example, in our hypothetical configuration file, the path to the
`x' setting is `application.window.pos.x'; the path to the `version'
setting is simply `version'; and the path to the `title' setting of the
second book in the `books' list is `application.books.[1].title'.

   The datatype of a value is determined from the format of the value
itself. If the value is enclosed in double quotes, it is treated as a
string. If it looks like an integer or floating point number, it is
treated as such. If it is one of the values `TRUE', `true', `FALSE', or
`false' (or any other mixed-case version of those tokens, e.g., `True'
or `FaLsE'), it is treated as a boolean. If it consists of a
comma-separated list of values enclosed in square brackets, it is
treated as an array. And if it consists of a comma-separated list of
values enclosed in parentheses, it is treated as a list. Any value
which does not meet any of these criteria is considered invalid and
results in a parse error.

   All names are case-sensitive. They may consist only of alphanumeric
characters, dashes (`-'), underscores (`_'), and asterisks (`*'), and
must begin with a letter or asterisk. No other characters are allowed.

   In C and C++, integer, 64-bit integer, floating point, and string
values are mapped to the types `int', `long long', `double', and `const
char *', respectively. The boolean type is mapped to `int' in C and
`bool' in C++.

   The following sections describe the elements of the configuration
file grammar in additional detail.


File: libconfig.info,  Node: Settings,  Next: Groups,  Up: Configuration Files

2.1 Settings
============

A setting has the form:

   name = value ;

   or:

   name : value ;

   The trailing semicolon is optional. Whitespace is not significant.

   The value may be a scalar value, an array, a group, or a list.


File: libconfig.info,  Node: Groups,  Next: Arrays,  Prev: Settings,  Up: Configuration Files

2.2 Groups
==========

A group has the form:

   {    settings ...  }

   Groups can contain any number of settings, but each setting must have
a unique name within the group.


File: libconfig.info,  Node: Arrays,  Next: Lists,  Prev: Groups,  Up: Configuration Files

2.3 Arrays
==========

An array has the form:

   [ value, value ... ]

   An array may have zero or more elements, but the elements must all be
scalar values of the same type.


File: libconfig.info,  Node: Lists,  Next: Integer Values,  Prev: Arrays,  Up: Configuration Files

2.4 Lists
=========

A list has the form:

   ( value, value ... )

   A list may have zero or more elements, each of which can be a scalar
value, an array, a group, or another list.


File: libconfig.info,  Node: Integer Values,  Next: 64-bit Integer Values,  Prev: Lists,  Up: Configuration Files

2.5 Integer Values
==================

Integers can be represented in one of two ways: as a series of one or
more decimal digits (`0' - `9'), with an optional leading sign
character (`+' or `-'); or as a hexadecimal value consisting of the
characters `0x' followed by a series of one or more hexadecimal digits
(`0' - `9', `A' - `F', `a' - `f').


File: libconfig.info,  Node: 64-bit Integer Values,  Next: Floating Point Values,  Prev: Integer Values,  Up: Configuration Files

2.6 64-bit Integer Values
=========================

Long long (64-bit) integers are represented identically to integers,
except that an 'L' character is appended to indicate a 64-bit value.
For example, `0L' indicates a 64-bit integer value 0.


File: libconfig.info,  Node: Floating Point Values,  Next: Boolean Values,  Prev: 64-bit Integer Values,  Up: Configuration Files

2.7 Floating Point Values
=========================

Floating point values consist of a series of one or more digits, one
decimal point, an optional leading sign character (`+' or `-'), and an
optional exponent. An exponent consists of the letter `E' or `e', an
optional sign character, and a series of one or more digits.


File: libconfig.info,  Node: Boolean Values,  Next: String Values,  Prev: Floating Point Values,  Up: Configuration Files

2.8 Boolean Values
==================

Boolean values may have one of the following values: `true', `false',
or any mixed-case variation thereof.


File: libconfig.info,  Node: String Values,  Next: Comments,  Prev: Boolean Values,  Up: Configuration Files

2.9 String Values
=================

String values consist of arbitrary text delimited by double quotes.
Literal double quotes can be escaped by preceding them with a
backslash: `\"'. The escape sequences `\\', `\f', `\n', `\r', and `\t'
are also recognized, and have the usual meaning.

   In addition, the `\x' escape sequence is supported; this sequence
must be followed by exactly two hexadecimal digits, which represent an
8-bit ASCII value. For example, `\xFF' represents the character with
ASCII code 0xFF.

   No other escape sequences are currently supported.

   Adjacent strings are automatically concatenated, as in C/C++ source
code. This is useful for formatting very long strings as sequences of
shorter strings. For example, the following constructs are equivalent:

   * `"The quick brown fox jumped over the lazy dog."'

   * `"The quick brown fox"'
     `" jumped over the lazy dog."'

   * `"The quick" /* comment */ " brown fox " // another comment'
     `"jumped over the lazy dog."'



File: libconfig.info,  Node: Comments,  Next: Include Directives,  Prev: String Values,  Up: Configuration Files

2.10 Comments
=============

Three types of comments are allowed within a configuration:

   * Script-style comments. All text beginning with a `#' character to
     the end of the line is ignored.

   * C-style comments. All text, including line breaks, between a
     starting `/*' sequence and an ending `*/' sequence is ignored.

   * C++-style comments. All text beginning with a `//' sequence to the
     end of the line is ignored.


   As expected, comment delimiters appearing within quoted strings are
treated as literal text.

   Comments are ignored when the configuration is read in, so they are
not treated as part of the configuration. Therefore if the
configuration is written back out to a stream, any comments that were
present in the original configuration will be lost.


File: libconfig.info,  Node: Include Directives,  Prev: Comments,  Up: Configuration Files

2.11 Include Directives
=======================

A configuration file may "include" the contents of another file using
an include directive. This directive has the effect of inlining the
contents of the named file at the point of inclusion.

   An include directive must appear on its own line in the input. It has
the form:

   @include "filename"

   Any backslashes or double quotes in the filename must be escaped as
`\\' and `\"', respectively.

   For example, consider the following two configuration files:

     # file: quote.cfg
     quote = "Criticism may not be agreeable, but it is necessary."
             " It fulfils the same function as pain in the human"
             " body. It calls attention to an unhealthy state of"
             " things.\n"
             "\t--Winston Churchill";

     # file: test.cfg
     info: {
       name = "Winston Churchill";
       @include "quote.cfg"
       country = "UK";
     };

   Include files may be nested to a maximum of 10 levels; exceeding this
limit results in a parse error.

   Like comments, include directives are not part of the configuration
file syntax. They are processed before the configuration itself is
parsed. Therefore, they are not preserved when the configuration is
written back out to a stream. There is presently no support for
programmatically inserting include directives into a configuration.


File: libconfig.info,  Node: The C API,  Next: The C++ API,  Prev: Configuration Files,  Up: Top

3 The C API
***********

This chapter describes the C library API. The type config_t represents
a configuration, and the type config_setting_t represents a
configuration setting.

   The boolean values `CONFIG_TRUE' and `CONFIG_FALSE' are macros
defined as `(1)' and `(0)', respectively.

 -- Function: void config_init (config_t * CONFIG)
 -- Function: void config_destroy (config_t * CONFIG)
     These functions initialize and destroy the configuration object
     CONFIG.

     `config_init()' initializes the config_t structure pointed to by
     CONFIG as a new, empty configuration.

     `config_destroy()' destroys the configuration CONFIG, deallocating
     all memory associated with the configuration, but does not attempt
     to deallocate the config_t structure itself.


 -- Function: int config_read (config_t * CONFIG, FILE * STREAM)
     This function reads and parses a configuration from the given
     STREAM into the configuration object CONFIG. It returns
     `CONFIG_TRUE' on success, or `CONFIG_FALSE' on failure; the
     `config_error_text()', `config_error_file()',
     `config_error_line()', and `config_error_type()' functions,
     described below, can be used to obtain information about the error.


 -- Function: int config_read_file (config_t * CONFIG,
          const char * FILENAME)
     This function reads and parses a configuration from the file named
     FILENAME into the configuration object CONFIG. It returns
     `CONFIG_TRUE' on success, or `CONFIG_FALSE' on failure; the
     `config_error_text()' and `config_error_line()' functions,
     described below, can be used to obtain information about the error.


 -- Function: int config_read_string (config_t * CONFIG,
          const char * STR)
     This function reads and parses a configuration from the string STR
     into the configuration object CONFIG. It returns `CONFIG_TRUE' on
     success, or `CONFIG_FALSE' on failure; the `config_error_text()'
     and `config_error_line()' functions, described below, can be used
     to obtain information about the error.


 -- Function: void config_write (const config_t * CONFIG, FILE * STREAM)
     This function writes the configuration CONFIG to the given STREAM.


 -- Function: int config_write_file (config_t * CONFIG,
          const char * FILENAME)
     This function writes the configuration CONFIG to the file named
     FILENAME. It returns `CONFIG_TRUE' on success, or `CONFIG_FALSE'
     on failure.


 -- Function: const char * config_error_text (const config_t * CONFIG)
 -- Function: const char * config_error_file (const config_t * CONFIG)
 -- Function: int config_error_line (const config_t * CONFIG)
     These functions, which are implemented as macros, return the text,
     filename, and line number of the parse error, if one occurred
     during a call to `config_read()', `config_read_string()', or
     `config_read_file()'. Storage for the strings returned by
     `config_error_text()' and `config_error_file()' are managed by the
     library and released automatically when the configuration is
     destroyed; these strings must not be freed by the caller. If the
     error occurred in text that was read from a string or stream,
     `config_error_file()' will return NULL.


 -- Function: config_error_t config_error_type (const config_t * CONFIG)
     This function, which is implemented as a macro, returns the type of
     error that occurred during the last call to one of the read or
     write functions. The CONFIG_ERROR_T type is an enumeration with the
     following values: `CONFIG_ERR_NONE', `CONFIG_ERR_FILE_IO',
     `CONFIG_ERR_PARSE'. These represent success, a file I/O error, and
     a parsing error, respectively.


 -- Function: void config_set_include_dir (config_t *CONFIG,
          const char *INCLUDE_DIR)
 -- Function: const char * config_get_include_dir
          (const config_t *CONFIG)
     `config_set_include_dir()' specifies the include directory,
     INCLUDE_DIR, relative to which the files specified in `@include'
     directives will be located for the configuration CONFIG. By
     default, there is no include directory, and all include files are
     expected to be relative to the current working directory. If
     INCLUDE_DIR is `NULL', the default behavior is reinstated.

     For example, if the include directory is set to `/usr/local/etc',
     the include directive `@include "configs/extra.cfg"' would include
     the file `/usr/local/etc/configs/extra.cfg'.

     `config_get_include_dir()' returns the current include directory
     for the configuration CONFIG, or `NULL' if none is set.


 -- Function: void config_set_auto_convert (config_t *CONFIG, int FLAG)
 -- Function: int config_get_auto_convert (const config_t *CONFIG)
     `config_set_auto_convert()' enables number auto-conversion for the
     configuration CONFIG if FLAG is non-zero, and disables it
     otherwise. When this feature is enabled, an attempt to retrieve a
     floating point setting's value into an integer (or vice versa), or
     store an integer to a floating point setting's value (or vice
     versa) will cause the library to silently perform the necessary
     conversion (possibly leading to loss of data), rather than
     reporting failure. By default this feature is disabled.

     `config_get_auto_convert()' returns `CONFIG_TRUE' if number
     auto-conversion is currently enabled for CONFIG; otherwise it
     returns `CONFIG_FALSE'.


 -- Function: void config_set_default_format (config_t * CONFIG,
          short FORMAT)
 -- Function: short config_get_default_format (config_t * CONFIG)
     These functions, which are implemented as macros, set and get the
     default external format for settings in the configuration CONFIG.
     If a non-default format has not been set for a setting with
     `config_setting_set_format()', this configuration-wide default
     format will be used instead when that setting is written to a file
     or stream.


 -- Function: void config_set_tab_width (config_t * CONFIG,
          unsigned short WIDTH)
 -- Function: unsigned short config_get_tab_width
          (const config_t * CONFIG)
     These functions, which are implemented as macros, set and get the
     tab width for the configuration CONFIG. The tab width affects the
     formatting of the configuration when it is written to a file or
     stream: each level of nesting is indented by WIDTH spaces, or by a
     single tab character if WIDTH is 0. The tab width has no effect on
     parsing.

     Valid tab widths range from 0 to 15. The default tab width is 2.


 -- Function: int config_lookup_int (const config_t * CONFIG,
          const char * PATH, int * VALUE)
 -- Function: int config_lookup_int64 (const config_t * CONFIG,
          const char * PATH, long long * VALUE)
 -- Function: int config_lookup_float (const config_t * CONFIG,
          const char * PATH, double * VALUE)
 -- Function: int config_lookup_bool (const config_t * CONFIG,
          const char * PATH, int * VALUE)
 -- Function: int config_lookup_string (const config_t * CONFIG,
          const char * PATH, const char ** VALUE)
     These functions look up the value of the setting in the
     configuration CONFIG specified by the path PATH. They store the
     value of the setting at VALUE and return `CONFIG_TRUE' on success.
     If the setting was not found or if the type of the value did not
     match the type requested, they leave the data pointed to by VALUE
     unmodified and return `CONFIG_FALSE'.

     Storage for the string returned by `config_lookup_string()' is
     managed by the library and released automatically when the setting
     is destroyed or when the setting's value is changed; the string
     must not be freed by the caller.


 -- Function: config_setting_t * config_lookup
          (const config_t * CONFIG, const char * PATH)
     This function locates the setting in the configuration CONFIG
     specified by the path PATH. It returns a pointer to the
     `config_setting_t' structure on success, or `NULL' if the setting
     was not found.


 -- Function: int config_setting_get_int
          (const config_setting_t * SETTING)
 -- Function: long long config_setting_get_int64
          (const config_setting_t * SETTING)
 -- Function: double config_setting_get_float
          (const config_setting_t * SETTING)
 -- Function: int config_setting_get_bool
          (const config_setting_t * SETTING)
 -- Function: const char * config_setting_get_string
          (const config_setting_t * SETTING)
     These functions return the value of the given SETTING. If the type
     of the setting does not match the type requested, a 0 or `NULL'
     value is returned. Storage for the string returned by
     `config_setting_get_string()' is managed by the library and
     released automatically when the setting is destroyed or when the
     setting's value is changed; the string must not be freed by the
     caller.


 -- Function: int config_setting_set_int (config_setting_t * SETTING,
          int VALUE)
 -- Function: int config_setting_set_int64 (config_setting_t * SETTING,
          long long VALUE)
 -- Function: int config_setting_set_float (config_setting_t * SETTING,
          double VALUE)
 -- Function: int config_setting_set_bool (config_setting_t * SETTING,
          int VALUE)
 -- Function: int config_setting_set_string
          (config_setting_t * SETTING, const char * VALUE)
     These functions set the value of the given SETTING to VALUE. On
     success, they return `CONFIG_TRUE'. If the setting does not match
     the type of the value, they return `CONFIG_FALSE'.
     `config_setting_set_string()' makes a copy of the passed string
     VALUE, so it may be subsequently freed or modified by the caller
     without affecting the value of the setting.


 -- Function: int config_setting_lookup_int
          (const config_setting_t * SETTING, const char * NAME,
          int * VALUE)
 -- Function: int config_setting_lookup_int64
          (const config_setting_t * SETTING, const char * NAME,
          long long * VALUE)
 -- Function: int config_setting_lookup_float
          (const config_setting_t * SETTING, const char * NAME,
          double * VALUE)
 -- Function: int config_setting_lookup_bool
          (const config_setting_t * SETTING, const char * NAME,
          int * VALUE)
 -- Function: int config_setting_lookup_string
          (const config_setting_t * SETTING, const char * NAME,
          const char ** VALUE)
     These functions look up the value of the child setting named NAME
     of the setting SETTING. They store the value at VALUE and return
     `CONFIG_TRUE' on success. If the setting was not found or if the
     type of the value did not match the type requested, they leave the
     data pointed to by VALUE unmodified and return `CONFIG_FALSE'.

     Storage for the string returned by
     `config_setting_lookup_string()' is managed by the library and
     released automatically when the setting is destroyed or when the
     setting's value is changed; the string must not be freed by the
     caller.


 -- Function: short config_setting_get_format
          (config_setting_t * SETTING)
 -- Function: int config_setting_set_format
          (config_setting_t * SETTING, short FORMAT)
     These functions get and set the external format for the setting
     SETTING.

     The FORMAT must be one of the constants `CONFIG_FORMAT_DEFAULT' or
     `CONFIG_FORMAT_HEX'. All settings support the
     `CONFIG_FORMAT_DEFAULT' format. The `CONFIG_FORMAT_HEX' format
     specifies hexadecimal formatting for integer values, and hence
     only applies to settings of type `CONFIG_TYPE_INT' and
     `CONFIG_TYPE_INT64'.  If FORMAT is invalid for the given setting,
     it is ignored.

     If a non-default format has not been set for the setting,
     `config_setting_get_format()' returns the default format for the
     configuration, as set by `config_set_default_format()'.

     `config_setting_set_format()' returns `CONFIG_TRUE' on success and
     `CONFIG_FALSE' on failure.


 -- Function: config_setting_t * config_setting_get_member
          (config_setting_t * SETTING, const char * NAME)
     This function fetches the child setting named NAME from the group
     SETTING. It returns the requested setting on success, or `NULL' if
     the setting was not found or if SETTING is not a group.


 -- Function: config_setting_t * config_setting_get_elem
          (const config_setting_t * SETTING, unsigned int INDEX)
     This function fetches the element at the given index INDEX in the
     setting SETTING, which must be an array, list, or group. It
     returns the requested setting on success, or `NULL' if INDEX is
     out of range or if SETTING is not an array, list, or group.


 -- Function: int config_setting_get_int_elem
          (const config_setting_t * SETTING, int INDEX)
 -- Function: long long config_setting_get_int64_elem
          (const config_setting_t * SETTING, int INDEX)
 -- Function: double config_setting_get_float_elem
          (const config_setting_t * SETTING, int INDEX)
 -- Function: int config_setting_get_bool_elem
          (const config_setting_t * SETTING, int INDEX)
 -- Function: const char * config_setting_get_string_elem
          (const config_setting_t * SETTING, int INDEX)
     These functions return the value at the specified index INDEX in
     the setting SETTING. If the setting is not an array or list, or if
     the type of the element does not match the type requested, or if
     INDEX is out of range, they return 0 or `NULL'. Storage for the
     string returned by `config_setting_get_string_elem()' is managed
     by the library and released automatically when the setting is
     destroyed or when its value is changed; the string must not be
     freed by the caller.

 -- Function: config_setting_t * config_setting_set_int_elem
          (config_setting_t * SETTING, int INDEX, int VALUE)
 -- Function: config_setting_t * config_setting_set_int64_elem
          (config_setting_t * SETTING, int INDEX, long long VALUE)
 -- Function: config_setting_t * config_setting_set_float_elem
          (config_setting_t * SETTING, int INDEX, double VALUE)
 -- Function: config_setting_t * config_setting_set_bool_elem
          (config_setting_t * SETTING, int INDEX, int VALUE)
 -- Function: config_setting_t * config_setting_set_string_elem
          (config_setting_t * SETTING, int INDEX, const char * VALUE)
     These functions set the value at the specified index INDEX in the
     setting SETTING to VALUE. If INDEX is negative, a new element is
     added to the end of the array or list. On success, these functions
     return a pointer to the setting representing the element. If the
     setting is not an array or list, or if the setting is an array and
     the type of the array does not match the type of the value, or if
     INDEX is out of range, they return `NULL'.
     `config_setting_set_string_elem()' makes a copy of the passed
     string VALUE, so it may be subsequently freed or modified by the
     caller without affecting the value of the setting.

 -- Function: config_setting_t * config_setting_add
          (config_setting_t * PARENT, const char * NAME, int TYPE)
     This function adds a new child setting or element to the setting
     PARENT, which must be a group, array, or list. If PARENT is an
     array or list, the NAME parameter is ignored and may be `NULL'.

     The function returns the new setting on success, or `NULL' if
     PARENT is not a group, array, or list; or if there is already a
     child setting of PARENT named NAME; or if TYPE is invalid. If TYPE
     is a scalar type, the new setting will have a default value of 0,
     0.0, `false', or `NULL', as appropriate.

 -- Function: int config_setting_remove (config_setting_t * PARENT,
          const char * NAME)
     This function removes and destroys the setting named NAME from the
     parent setting PARENT, which must be a group. Any child settings
     of the setting are recursively destroyed as well.

     The function returns `CONFIG_TRUE' on success. If PARENT is not a
     group, or if it has no setting with the given name, it returns
     `CONFIG_FALSE'.


 -- Function: int config_setting_remove_elem
          (config_setting_t * PARENT, unsigned int INDEX)
     This function removes the child setting at the given index INDEX
     from the setting PARENT, which must be a group, list, or array. Any
     child settings of the removed setting are recursively destroyed as
     well.

     The function returns `CONFIG_TRUE' on success. If PARENT is not a
     group, list, or array, or if INDEX is out of range, it returns
     `CONFIG_FALSE'.


 -- Function: config_setting_t * config_root_setting
          (const config_t * CONFIG)
     This function returns the root setting for the configuration
     CONFIG. The root setting is a group.


 -- Function: const char * config_setting_name
          (const config_setting_t * SETTING)
     This function returns the name of the given SETTING, or `NULL' if
     the setting has no name. Storage for the returned string is
     managed by the library and released automatically when the setting
     is destroyed; the string must not be freed by the caller.


 -- Function: config_setting_t * config_setting_parent
          (const config_setting_t * SETTING)
     This function returns the parent setting of the given SETTING, or
     `NULL' if SETTING is the root setting.


 -- Function: int config_setting_is_root
          (const config_setting_t * SETTING)
     This function returns `CONFIG_TRUE' if the given SETTING is the
     root setting, and `CONFIG_FALSE' otherwise.


 -- Function: int config_setting_index
          (const config_setting_t * SETTING)
     This function returns the index of the given SETTING within its
     parent setting. If SETTING is the root setting, this function
     returns -1.


 -- Function: int config_setting_length
          (const config_setting_t * SETTING)
     This function returns the number of settings in a group, or the
     number of elements in a list or array. For other types of
     settings, it returns 0.


 -- Function: int config_setting_type (const config_setting_t * SETTING)
     This function returns the type of the given SETTING. The return
     value is one of the constants `CONFIG_TYPE_INT',
     `CONFIG_TYPE_INT64', `CONFIG_TYPE_FLOAT', `CONFIG_TYPE_STRING',
     `CONFIG_TYPE_BOOL', `CONFIG_TYPE_ARRAY', `CONFIG_TYPE_LIST', or
     `CONFIG_TYPE_GROUP'.


 -- Function: int config_setting_is_group
          (const config_setting_t * SETTING)
 -- Function: int config_setting_is_array
          (const config_setting_t * SETTING)
 -- Function: int config_setting_is_list
          (const config_setting_t * SETTING)
     These convenience functions, which are implemented as macros, test
     if the setting SETTING is of a given type. They return
     `CONFIG_TRUE' or `CONFIG_FALSE'.


 -- Function: int config_setting_is_aggregate
          (const config_setting_t * SETTING)
 -- Function: int config_setting_is_scalar
          (const config_setting_t * SETTING)
 -- Function: int config_setting_is_number
          (const config_setting_t * SETTING)
     These convenience functions, which are implemented as macros, test
     if the setting SETTING is of an aggregate type (a group, array, or
     list), of a scalar type (integer, 64-bit integer, floating point,
     boolean, or string), and of a number (integer, 64-bit integer, or
     floating point), respectively. They return `CONFIG_TRUE' or
     `CONFIG_FALSE'.


 -- Function: const char * config_setting_source_file
          (const config_setting_t * SETTING)
     This function returns the name of the file from which the setting
     SETTING was read, or NULL if the setting was not read from a file.
     This information is useful for reporting application-level errors.
     Storage for the returned string is managed by the library and
     released automatically when the configuration is destroyed; the
     string must not be freed by the caller.


 -- Function: unsigned int config_setting_source_line
          (const config_setting_t * SETTING)
     This function returns the line number of the configuration file or
     stream at which the setting SETTING was read, or 0 if no line
     number is available. This information is useful for reporting
     application-level errors.


 -- Function: void config_setting_set_hook (config_setting_t * SETTING,
          void * HOOK)
 -- Function: void * config_setting_get_hook
          (const config_setting_t * SETTING)
     These functions make it possible to attach arbitrary data to each
     setting structure, for instance a "wrapper" or "peer" object
     written in another programming language. The destructor function,
     if one has been supplied via a call to `config_set_destructor()',
     will be called by the library to dispose of this data when the
     setting itself is destroyed. There is no default destructor.


 -- Function: void config_set_destructor (config_t * CONFIG,
          void (* DESTRUCTOR)(void *))
     This function assigns the destructor function DESTRUCTOR for the
     configuration CONFIG. This function accepts a single `void *'
     argument and has no return value. See `config_setting_set_hook()'
     above for more information.



File: libconfig.info,  Node: The C++ API,  Next: Example Programs,  Prev: The C API,  Up: Top

4 The C++ API
*************

This chapter describes the C++ library API. The class `Config'
represents a configuration, and the class `Setting' represents a
configuration setting. Note that by design, neither of these classes
provides a public copy constructor or assignment operator. Therefore,
instances of these classes may only be passed between functions via
references or pointers.

   The library defines a group of exceptions, all of which extend the
common base exception `ConfigException'.

   A `SettingTypeException' is thrown when the type of a setting's
value does not match the type requested.

   A `SettingNotFoundException' is thrown when a setting is not found.

   A `SettingNameException' is thrown when an attempt is made to add a
new setting with a non-unique or invalid name.

   A `ParseException' is thrown when a parse error occurs while reading
a configuration from a stream.

   A `FileIOException' is thrown when an I/O error occurs while
reading/writing a configuration from/to a file.

   `SettingTypeException', `SettingNotFoundException', and
`SettingNameException' all extend the common base exception
`SettingException', which provides the following method:

 -- Method on SettingException: const char * getPath ()
     Returns the path to the setting associated with the exception, or
     `NULL' if there is no applicable path.


   The remainder of this chapter describes the methods for manipulating
configurations and configuration settings.

 -- Method on Config:  Config ()
 -- Method on Config:  ~Config ()
     These methods create and destroy `Config' objects.


 -- Method on Config: void read (FILE * STREAM)
 -- Method on Config: void write (FILE * STREAM)
     The `read()' method reads and parses a configuration from the given
     STREAM. A `ParseException' is thrown if a parse error occurs.

     The `write()' method writes the configuration to the given STREAM.


 -- Method on Config: void readFile (const char * FILENAME)
 -- Method on Config: void writeFile (const char * FILENAME)
     The `readFile()' method reads and parses a configuration from the
     file named FILENAME. A `ParseException' is thrown if a parse error
     occurs. A `FileIOException' is thrown if the file cannot be read.

     The `writeFile()' method writes the configuration to the file
     named FILENAME. A `FileIOException' is thrown if the file cannot
     be written.


 -- Method on Config: void readString (const char * STR)
 -- Method on Config: void readString (const std::string &STR)
     These methods read and parse a configuration from the string STR.
     A `ParseException' is thrown if a parse error occurs.


 -- Method on ParseException: const char * getError ()
 -- Method on ParseException: const char * getFile ()
 -- Method on ParseException: int getLine ()
     If a call to `readFile()', `readString()', or `read()' resulted in
     a `ParseException', these methods can be called on the exception
     object to obtain the text, filename, and line number of the parse
     error. Storage for the strings returned by `getError()' and
     `getFile()' are managed by the library; the strings must not be
     freed by the caller.


 -- Method on Config: void setIncludeDir (const char *INCLUDEDIR)
 -- Method on Config: const char * getIncludeDir ()
     `setIncludeDir()' specifies the include directory, INCLUDEDIR,
     relative to which the files specified in `@include' directives
     will be located for the configuration. By default, there is no
     include directory, and all include files are expected to be
     relative to the current working directory. If INCLUDEDIR is
     `NULL', the default behavior is reinstated.

     For example, if the include directory is set to `/usr/local/etc',
     the include directive `@include "configs/extra.cfg"' would include
     the file `/usr/local/etc/configs/extra.cfg'.

     `getIncludeDir()' returns the current include directory for the
     configuration, or `NULL' if none is set.


 -- Method on Config: void setAutoConvert (bool FLAG)
 -- Method on Config: bool getAutoConvert ()
     `setAutoConvert()' enables number auto-conversion for the
     configuration if FLAG is `true', and disables it otherwise. When
     this feature is enabled, an attempt to assign a floating point
     setting to an integer (or vice versa), or assign an integer to a
     floating point setting (or vice versa) will cause the library to
     silently perform the necessary conversion (possibly leading to
     loss of data), rather than throwing a `SettingTypeException'. By
     default this feature is disabled.

     `getAutoConvert()' returns `true' if number auto-conversion is
     currently enabled for the configuration; otherwise it returns
     `false'.


 -- Method on Config: void setDefaultFormat (Setting::Format FORMAT)
 -- Method on Config: Setting::Format getDefaultFormat ()
     These methods set and get the default external format for settings
     in the configuration. If a non-default format has not been set for
     a setting with `Setting::setFormat()', this configuration-wide
     default format will be used instead when that setting is written
     to a file or stream.


 -- Method on Config: void setTabWidth (unsigned short WIDTH)
 -- Method on Config: unsigned short getTabWidth ()
     These methods set and get the tab width for the configuration. The
     tab width affects the formatting of the configuration when it is
     written to a file or stream: each level of nesting is indented by
     WIDTH spaces, or by a single tab character if WIDTH is 0. The tab
     width has no effect on parsing.

     Valid tab widths range from 0 to 15. The default tab width is 2.


 -- Method on Config: Setting & getRoot ()
     This method returns the root setting for the configuration, which
     is a group.


 -- Method on Config: Setting & lookup (const std::string &PATH)
 -- Method on Config: Setting & lookup (const char * PATH)
     These methods locate the setting specified by the path PATH. If
     the requested setting is not found, a `SettingNotFoundException' is
     thrown.


 -- Method on Config: bool exists (const std::string &PATH)
 -- Method on Config: bool exists (const char *PATH)
     These methods test if a setting with the given PATH exists in the
     configuration. They return `true' if the setting exists, and
     `false' otherwise. These methods do not throw exceptions.


 -- Method on Config: bool lookupValue (const char *PATH, bool &VALUE)
 -- Method on Config: bool lookupValue (const std::string &PATH,
          bool &VALUE)
 -- Method on Config: bool lookupValue (const char *PATH, int &VALUE)
 -- Method on Config: bool lookupValue (const std::string &PATH,
          int &VALUE)
 -- Method on Config: bool lookupValue (const char *PATH,
          unsigned int &VALUE)
 -- Method on Config: bool lookupValue (const std::string &PATH,
          unsigned int &VALUE)
 -- Method on Config: bool lookupValue (const char *PATH,
          long long &VALUE)
 -- Method on Config: bool lookupValue (const std::string &PATH,
          long long &VALUE)
 -- Method on Config: bool lookupValue (const char *PATH, float &VALUE)
 -- Method on Config: bool lookupValue (const std::string &PATH,
          float &VALUE)
 -- Method on Config: bool lookupValue (const char *PATH, double &VALUE)
 -- Method on Config: bool lookupValue (const std::string &PATH,
          double &VALUE)
 -- Method on Config: bool lookupValue (const char *PATH,
          const char *&VALUE)
 -- Method on Config: bool lookupValue (const std::string &PATH,
          const char *&VALUE)
 -- Method on Config: bool lookupValue (const char *PATH,
          std::string &VALUE)
 -- Method on Config: bool lookupValue (const std::string &PATH,
          std::string &VALUE)
     These are convenience methods for looking up the value of a setting
     with the given PATH. If the setting is found and is of an
     appropriate type, the value is stored in VALUE and the method
     returns `true'. Otherwise, VALUE is left unmodified and the method
     returns `false'. These methods do not throw exceptions.

     Storage for const char * values is managed by the library and
     released automatically when the setting is destroyed or when its
     value is changed; the string must not be freed by the caller. For
     safety and convenience, always assigning string values to a
     `std::string' is suggested.

     Since these methods have boolean return values and do not throw
     exceptions, they can be used within boolean logic expressions. The
     following example presents a concise way to look up three values
     at once and perform error handling if any of them are not found or
     are of the wrong type:


          int var1;
          double var2;
          const char *var3;

          if(config.lookupValue("values.var1", var1)
             && config.lookupValue("values.var2", var2)
             && config.lookupValue("values.var3", var3))
          {
            // use var1, var2, var3
          }
          else
          {
            // error handling here
          }

     This approach also takes advantage of the short-circuit evaluation
     rules of C++, e.g., if the first lookup fails (returning `false'),
     the remaining lookups are skipped entirely.


 -- Method on Setting:  operator bool ()
 -- Method on Setting:  operator int ()
 -- Method on Setting:  operator unsigned int ()
 -- Method on Setting:  operator long ()
 -- Method on Setting:  operator unsigned long ()
 -- Method on Setting:  operator long long ()
 -- Method on Setting:  operator unsigned long long ()
 -- Method on Setting:  operator float ()
 -- Method on Setting:  operator double ()
 -- Method on Setting:  operator const char * ()
 -- Method on Setting:  operator std::string ()
 -- Method on Setting: const char * c_str ()
     These cast operators allow a `Setting' object to be assigned to a
     variable of type bool if it is of type `TypeBoolean'; int,
     unsigned int; `long long' or `unsigned long long' if it is of type
     `TypeInt64', float or double if it is of type `TypeFloat'; or
     const char * or std::string if it is of type `TypeString'.

     Values of type `TypeInt' or `TypeInt64' may be assigned to
     variables of type long, or unsigned long, depending on the sizes
     of those types on the host system.

     Storage for const char * return values is managed by the library
     and released automatically when the setting is destroyed or when
     its value is changed; the string must not be freed by the caller.
     For safety and convenience, always assigning string return values
     to a `std::string' is suggested.

     The following examples demonstrate this usage:

          long width = config.lookup("application.window.size.w");

          bool splashScreen = config.lookup("application.splash_screen");

          std::string title = config.lookup("application.window.title");

     Note that certain conversions can lead to loss of precision or
     clipping of values, e.g., assigning a negative value to an unsigned
     int (in which case the value will be treated as 0), or a
     double-precision value to a float. The library does not treat
     these lossy conversions as errors.

     Perhaps surprisingly, the following code in particular will cause a
     compiler error:

          std::string title;
          .
          .
          .
          title = config.lookup("application.window.title");

     This is because the assignment operator of `std::string' is being
     invoked with a `Setting &' as an argument. The compiler is unable
     to make an implicit conversion because both the `const char *' and
     the `std::string' cast operators of `Setting' are equally
     appropriate. This is not a bug in libconfig; providing only the
     `const char *' cast operator would resolve this particular
     ambiguity, but would cause assignments to `std::string' like the
     one in the previous example to produce a compiler error. (To
     understand why, see section 11.4.1 of The C++ Programming
     Language.)

     The solution to this problem is to use an explicit conversion that
     avoids the construction of an intermediate `std::string' object,
     as follows:

          std::string title;
          .
          .
          .
          title = (const char *)config.lookup("application.window.title");

     Or, alternatively, use the `c_str()' method, which has the same
     effect:

          std::string title;
          .
          .
          .
          title = config.lookup("application.window.title").c_str();

     If the assignment is invalid due to a type mismatch, a
     `SettingTypeException' is thrown.


 -- Method on Setting: Setting & operator= (bool VALUE)
 -- Method on Setting: Setting & operator= (int VALUE)
 -- Method on Setting: Setting & operator= (long VALUE)
 -- Method on Setting: Setting & operator= (const long long &VALUE)
 -- Method on Setting: Setting & operator= (float VALUE)
 -- Method on Setting: Setting & operator= (const double &VALUE)
 -- Method on Setting: Setting & operator= (const char *VALUE)
 -- Method on Setting: Setting & operator= (const std::string &VALUE)
     These assignment operators allow values of type bool, int, long,
     long long, float, double, const char *, and std::string to be
     assigned to a setting. In the case of strings, the library makes a
     copy of the passed string VALUE, so it may be subsequently freed
     or modified by the caller without affecting the value of the
     setting.

     The following example code looks up a (presumably) integer setting
     and changes its value:

          Setting &setting = config.lookup("application.window.size.w");
          setting = 1024;

     If the assignment is invalid due to a type mismatch, a
     `SettingTypeException' is thrown.


 -- Method on Setting: Setting & operator[] (int INDEX)
 -- Method on Setting: Setting & operator[] (const std::string &NAME)
 -- Method on Setting: Setting & operator[] (const char *NAME)
     A `Setting' object may be subscripted with an integer index INDEX
     if it is an array or list, or with either a string NAME or an
     integer index INDEX if it is a group. For example, the following
     code would produce the string `Last Name' when applied to the
     example configuration in *note Configuration Files::.

          Setting& setting = config.lookup("application.misc");
          const char *s = setting["columns"][0];

     If the setting is not an array, list, or group, a
     `SettingTypeException' is thrown. If the subscript (INDEX or NAME)
     does not refer to a valid element, a `SettingNotFoundException' is
     thrown.

     Iterating over a group's child settings with an integer index will
     return the settings in the same order that they appear in the
     configuration.


 -- Method on Setting: bool lookupValue (const char *NAME, bool &VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          bool &VALUE)
 -- Method on Setting: bool lookupValue (const char *NAME, int &VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          int &VALUE)
 -- Method on Setting: bool lookupValue (const char *NAME,
          unsigned int &VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          unsigned int &VALUE)
 -- Method on Setting: bool lookupValue (const char *NAME,
          long long &VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          long long &VALUE)
 -- Method on Setting: bool lookupValue (const char *NAME,
          unsigned long long &VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          unsigned long long &VALUE)
 -- Method on Setting: bool lookupValue (const char *NAME, float &VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          float &VALUE)
 -- Method on Setting: bool lookupValue (const char *NAME,
          double &VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          double &VALUE)
 -- Method on Setting: bool lookupValue (const char *NAME,
          const char *&VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          const char *&VALUE)
 -- Method on Setting: bool lookupValue (const char *NAME,
          std::string &VALUE)
 -- Method on Setting: bool lookupValue (const std::string &NAME,
          std::string &VALUE)
     These are convenience methods for looking up the value of a child
     setting with the given NAME. If the setting is found and is of an
     appropriate type, the value is stored in VALUE and the method
     returns `true'. Otherwise, VALUE is left unmodified and the method
     returns `false'. These methods do not throw exceptions.

     Storage for const char * values is managed by the library and
     released automatically when the setting is destroyed or when its
     value is changed; the string must not be freed by the caller. For
     safety and convenience, always assigning string values to a
     `std::string' is suggested.

     Since these methods have boolean return values and do not throw
     exceptions, they can be used within boolean logic expressions. The
     following example presents a concise way to look up three values
     at once and perform error handling if any of them are not found or
     are of the wrong type:


          int var1;
          double var2;
          const char *var3;

          if(setting.lookupValue("var1", var1)
             && setting.lookupValue("var2", var2)
             && setting.lookupValue("var3", var3))
          {
            // use var1, var2, var3
          }
          else
          {
            // error handling here
          }

     This approach also takes advantage of the short-circuit evaluation
     rules of C++, e.g., if the first lookup fails (returning `false'),
     the remaining lookups are skipped entirely.


 -- Method on Setting: Setting & add (const std::string &NAME,
          Setting::Type TYPE)
 -- Method on Setting: Setting & add (const char *NAME,
          Setting::Type TYPE)
     These methods add a new child setting with the given NAME and TYPE
     to the setting, which must be a group. They return a reference to
     the new setting. If the setting already has a child setting with
     the given name, or if the name is invalid, a
     `SettingNameException' is thrown. If the setting is not a group, a
     `SettingTypeException' is thrown.

     Once a setting has been created, neither its name nor type can be
     changed.


 -- Method on Setting: Setting & add (Setting::Type TYPE)
     This method adds a new element to the setting, which must be of
     type `TypeArray' or `TypeList'. If the setting is an array which
     currently has zero elements, the TYPE parameter (which must be
     `TypeInt', `TypeInt64', `TypeFloat', `TypeBool', or `TypeString')
     determines the type for the array; otherwise it must match the
     type of the existing elements in the array.

     The method returns the new setting on success. If TYPE is a scalar
     type, the new setting will have a default value of 0, 0.0,
     `false', or `NULL', as appropriate.

     The method throws a `SettingTypeException' if the setting is not
     an array or list, or if TYPE is invalid.


 -- Method on Setting: void remove (const std::string &NAME)
 -- Method on Setting: void remove (const char *NAME)
     These methods remove the child setting with the given NAME from
     the setting, which must be a group. Any child settings of the
     removed setting are recursively destroyed as well.

     If the setting is not a group, a `SettingTypeException' is thrown.
     If the setting does not have a child setting with the given name,
     a `SettingNotFoundException' is thrown.


 -- Method on Setting: void remove (unsigned int INDEX)
     This method removes the child setting at the given index INDEX from
     the setting, which must be a group, list, or array. Any child
     settings of the removed setting are recursively destroyed as well.

     If the setting is not a group, list, or array, a
     `SettingTypeException' is thrown.  If INDEX is out of range, a
     `SettingNotFoundException' is thrown.


 -- Method on Setting: const char * getName ()
     This method returns the name of the setting, or `NULL' if the
     setting has no name. Storage for the returned string is managed by
     the library and released automatically when the setting is
     destroyed; the string must not be freed by the caller. For safety
     and convenience, consider assigning the return value to a
     `std::string'.


 -- Method on Setting: std::string getPath ()
     This method returns the complete dot-separated path to the
     setting. Settings which do not have a name (list and array
     elements) are represented by their index in square brackets.


 -- Method on Setting: Setting & getParent ()
     This method returns the parent setting of the setting. If the
     setting is the root setting, a `SettingNotFoundException' is
     thrown.


 -- Method on Setting: bool isRoot ()
     This method returns `true' if the setting is the root setting, and
     `false' otherwise.


 -- Method on Setting: int getIndex ()
     This method returns the index of the setting within its parent
     setting. When applied to the root setting, this method returns -1.


 -- Method on Setting: Setting::Type getType ()
     This method returns the type of the setting. The `Setting::Type'
     enumeration consists of the following constants: `TypeInt',
     `TypeInt64', `TypeFloat', `TypeString', `TypeBoolean',
     `TypeArray', `TypeList', and `TypeGroup'.


 -- Method on Setting: Setting::Format getFormat ()
 -- Method on Setting: void setFormat (Setting::Format FORMAT)
     These methods get and set the external format for the setting.

     The SETTING::FORMAT enumeration consists of the following
     constants: `FormatDefault' and `FormatHex'. All settings support
     the `FormatDefault' format. The `FormatHex' format specifies
     hexadecimal formatting for integer values, and hence only applies
     to settings of type `TypeInt' and `TypeInt64'. If FORMAT is
     invalid for the given setting, it is ignored.


 -- Method on Setting: bool exists (const std::string &NAME)
 -- Method on Setting: bool exists (const char *NAME)
     These methods test if the setting has a child setting with the
     given NAME. They return `true' if the setting exists, and `false'
     otherwise. These methods do not throw exceptions.


 -- Method on Setting: int getLength ()
     This method returns the number of settings in a group, or the
     number of elements in a list or array. For other types of
     settings, it returns 0.


 -- Method on Setting: bool isGroup ()
 -- Method on Setting: bool isArray ()
 -- Method on Setting: bool isList ()
     These convenience methods test if a setting is of a given type.


 -- Method on Setting: bool isAggregate ()
 -- Method on Setting: bool isScalar ()
 -- Method on Setting: bool isNumber ()
     These convenience methods test if a setting is of an aggregate
     type (a group, array, or list), of a scalar type (integer, 64-bit
     integer, floating point, boolean, or string), and of a number
     (integer, 64-bit integer, or floating point), respectively.


 -- Method on Setting: const char * getSourceFile ()
     This function returns the name of the file from which the setting
     was read, or NULL if the setting was not read from a file. This
     information is useful for reporting application-level errors.
     Storage for the returned string is managed by the library and
     released automatically when the configuration is destroyed; the
     string must not be freed by the caller.


 -- Method on Setting: unsigned int getSourceLine ()
     This function returns the line number of the configuration file or
     stream at which the setting SETTING was read, or 0 if no line
     number is available. This information is useful for reporting
     application-level errors.



File: libconfig.info,  Node: Example Programs,  Next: Configuration File Grammar,  Prev: The C++ API,  Up: Top

5 Example Programs
******************

Practical example programs that illustrate how to use libconfig from
both C and C++ are included in the `examples' subdirectory of the
distribution. These examples include:

`examples/c/example1.c'
     An example C program that reads a configuration from an existing
     file `example.cfg' (also located in `examples/c') and displays
     some of its contents.

`examples/c++/example1.cpp'
     The C++ equivalent of `example1.c'.

`examples/c/example2.c'
     An example C program that reads a configuration from an existing
     file `example.cfg' (also located in `examples/c'), adds new
     settings to the configuration, and writes the updated
     configuration to another file.

`examples/c++/example2.cpp'
     The C++ equivalent of `example2.c'

`examples/c/example3.c'
     An example C program that constructs a new configuration in memory
     and writes it to a file.

`examples/c++/example3.cpp'
     The C++ equivalent of `example3.c'



File: libconfig.info,  Node: Configuration File Grammar,  Next: License,  Prev: Example Programs,  Up: Top

6 Configuration File Grammar
****************************

Below is the BNF grammar for configuration files. Comments and include
directives are not part of the grammar, so they are not included here.


     configuration = setting-list | empty

     setting-list = setting | setting-list setting

     setting = name (":" | "=") value (";" | "," | empty)

     value = scalar-value | array | list | group

     value-list = value | value-list "," value

     scalar-value = boolean | integer | integer64 | hex | hex64 | float
                    | string

     scalar-value-list = scalar-value | scalar-value-list "," scalar-value

     array = "[" (scalar-value-list | empty) "]"

     list = "(" (value-list | empty) ")"

     group = "{" (setting-list | empty) "}"

     empty =



   Terminals are defined below as regular expressions:

`boolean'       `([Tt][Rr][Uu][Ee])|([Ff][Aa][Ll][Ss][Ee])'
`string'        `\"([^\"\\]|\\.)*\"'
`name'          `[A-Za-z\*][-A-Za-z0-9_\*]*'
`integer'       `[-+]?[0-9]+'
`integer64'     `[-+]?[0-9]+L(L)?'
`hex'           `0[Xx][0-9A-Fa-f]+'
`hex64'         `0[Xx][0-9A-Fa-f]+L(L)?'
`float'         `([-+]?([0-9]*)?\.[0-9]*([eE][-+]?[0-9]+)?)|([-+]([0-9]+)(\.[0-9]*)?[eE][-+]?[0-9]+)'


File: libconfig.info,  Node: License,  Next: Function Index,  Prev: Configuration File Grammar,  Up: Top

Appendix A License
******************

                   GNU LESSER GENERAL PUBLIC LICENSE
                      Version 2.1, February 1999


   Copyright (C) 1991, 1999 Free Software Foundation, Inc., 59 Temple
Place, Suite 330, Boston, MA  02111-1307  USA

   Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

   [This is the first released version of the Lesser GPL.  It also
counts as the successor of the GNU Library Public License, version 2,
hence the version number 2.1.]


                               Preamble

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   This license, the Lesser General Public License, applies to some
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it too, but we suggest you first think carefully about whether this
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   When we speak of free software, we are referring to freedom of use,
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   Although the Lesser General Public License is Less protective of the
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    TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION


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effectively convey the exclusion of warranty; and each file should have
at least the "copyright" line and a pointer to where the full notice is
found.


<one line to give the library's name and a brief idea of what it does.>
Copyright (C) <year>  <name of author>

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA

   Also add information on how to contact you by electronic and paper
mail.

   You should also get your employer (if you work as a programmer) or
your school, if any, to sign a "copyright disclaimer" for the library,
if necessary.  Here is a sample; alter the names:


Yoyodyne, Inc., hereby disclaims all copyright interest in the
library `Frob' (a library for tweaking knobs) written by James Random Hacker.

<signature of Ty Coon>, 1 April 1990
Ty Coon, President of Vice

   That's all there is to it!


File: libconfig.info,  Node: Function Index,  Next: Type Index,  Prev: License,  Up: Top

Function Index
**************

[index]
* Menu:

* add on Setting:                        The C++ API.         (line 428)
* c_str on Setting:                      The C++ API.         (line 234)
* Config on Config:                      The C++ API.         (line  43)
* config_destroy:                        The C API.           (line  15)
* config_error_file:                     The C API.           (line  66)
* config_error_line:                     The C API.           (line  67)
* config_error_text:                     The C API.           (line  65)
* config_error_type:                     The C API.           (line  79)
* config_get_auto_convert:               The C API.           (line 108)
* config_get_default_format:             The C API.           (line 125)
* config_get_include_dir:                The C API.           (line  91)
* config_get_tab_width:                  The C API.           (line 137)
* config_init:                           The C API.           (line  14)
* config_lookup:                         The C API.           (line 172)
* config_lookup_bool:                    The C API.           (line 155)
* config_lookup_float:                   The C API.           (line 153)
* config_lookup_int:                     The C API.           (line 149)
* config_lookup_int64:                   The C API.           (line 151)
* config_lookup_string:                  The C API.           (line 157)
* config_read:                           The C API.           (line  27)
* config_read_file:                      The C API.           (line  37)
* config_read_string:                    The C API.           (line  46)
* config_root_setting:                   The C API.           (line 358)
* config_set_auto_convert:               The C API.           (line 107)
* config_set_default_format:             The C API.           (line 124)
* config_set_destructor:                 The C API.           (line 461)
* config_set_include_dir:                The C API.           (line  89)
* config_set_tab_width:                  The C API.           (line 135)
* config_setting_add:                    The C API.           (line 323)
* config_setting_get_bool:               The C API.           (line 186)
* config_setting_get_bool_elem:          The C API.           (line 289)
* config_setting_get_elem:               The C API.           (line 275)
* config_setting_get_float:              The C API.           (line 184)
* config_setting_get_float_elem:         The C API.           (line 287)
* config_setting_get_format:             The C API.           (line 245)
* config_setting_get_hook:               The C API.           (line 451)
* config_setting_get_int:                The C API.           (line 180)
* config_setting_get_int64:              The C API.           (line 182)
* config_setting_get_int64_elem:         The C API.           (line 285)
* config_setting_get_int_elem:           The C API.           (line 283)
* config_setting_get_member:             The C API.           (line 268)
* config_setting_get_string:             The C API.           (line 188)
* config_setting_get_string_elem:        The C API.           (line 291)
* config_setting_index:                  The C API.           (line 384)
* config_setting_is_aggregate:           The C API.           (line 417)
* config_setting_is_array:               The C API.           (line 408)
* config_setting_is_group:               The C API.           (line 406)
* config_setting_is_list:                The C API.           (line 410)
* config_setting_is_number:              The C API.           (line 421)
* config_setting_is_root:                The C API.           (line 378)
* config_setting_is_scalar:              The C API.           (line 419)
* config_setting_length:                 The C API.           (line 391)
* config_setting_lookup_bool:            The C API.           (line 227)
* config_setting_lookup_float:           The C API.           (line 224)
* config_setting_lookup_int:             The C API.           (line 218)
* config_setting_lookup_int64:           The C API.           (line 221)
* config_setting_lookup_string:          The C API.           (line 230)
* config_setting_name:                   The C API.           (line 364)
* config_setting_parent:                 The C API.           (line 372)
* config_setting_remove:                 The C API.           (line 335)
* config_setting_remove_elem:            The C API.           (line 346)
* config_setting_set_bool:               The C API.           (line 205)
* config_setting_set_bool_elem:          The C API.           (line 308)
* config_setting_set_float:              The C API.           (line 203)
* config_setting_set_float_elem:         The C API.           (line 306)
* config_setting_set_format:             The C API.           (line 247)
* config_setting_set_hook:               The C API.           (line 449)
* config_setting_set_int:                The C API.           (line 199)
* config_setting_set_int64:              The C API.           (line 201)
* config_setting_set_int64_elem:         The C API.           (line 304)
* config_setting_set_int_elem:           The C API.           (line 302)
* config_setting_set_string:             The C API.           (line 207)
* config_setting_set_string_elem:        The C API.           (line 310)
* config_setting_source_file:            The C API.           (line 431)
* config_setting_source_line:            The C API.           (line 441)
* config_setting_type:                   The C API.           (line 397)
* config_write:                          The C API.           (line  54)
* config_write_file:                     The C API.           (line  59)
* exists on Config:                      The C++ API.         (line 149)
* exists on Setting:                     The C++ API.         (line 529)
* getAutoConvert on Config:              The C++ API.         (line 102)
* getDefaultFormat on Config:            The C++ API.         (line 118)
* getError on ParseException:            The C++ API.         (line  73)
* getFile on ParseException:             The C++ API.         (line  74)
* getFormat on Setting:                  The C++ API.         (line 517)
* getIncludeDir on Config:               The C++ API.         (line  85)
* getIndex on Setting:                   The C++ API.         (line 505)
* getLength on Setting:                  The C++ API.         (line 536)
* getLine on ParseException:             The C++ API.         (line  75)
* getName on Setting:                    The C++ API.         (line 479)
* getParent on Setting:                  The C++ API.         (line 494)
* getPath on Setting:                    The C++ API.         (line 488)
* getPath on SettingException:           The C++ API.         (line  35)
* getRoot on Config:                     The C++ API.         (line 137)
* getSourceFile on Setting:              The C++ API.         (line 557)
* getSourceLine on Setting:              The C++ API.         (line 566)
* getTabWidth on Config:                 The C++ API.         (line 127)
* getType on Setting:                    The C++ API.         (line 510)
* isAggregate on Setting:                The C++ API.         (line 548)
* isArray on Setting:                    The C++ API.         (line 543)
* isGroup on Setting:                    The C++ API.         (line 542)
* isList on Setting:                     The C++ API.         (line 544)
* isNumber on Setting:                   The C++ API.         (line 550)
* isRoot on Setting:                     The C++ API.         (line 500)
* isScalar on Setting:                   The C++ API.         (line 549)
* LIBCONFIG_VER_MAJOR:                   Version Test Macros. (line   9)
* LIBCONFIG_VER_MINOR:                   Version Test Macros. (line  10)
* LIBCONFIG_VER_REVISION:                Version Test Macros. (line  11)
* LIBCONFIGXX_VER_MAJOR:                 Version Test Macros. (line  28)
* LIBCONFIGXX_VER_MINOR:                 Version Test Macros. (line  29)
* LIBCONFIGXX_VER_REVISION:              Version Test Macros. (line  30)
* lookup on Config:                      The C++ API.         (line 142)
* lookupValue on Config:                 The C++ API.         (line 156)
* lookupValue on Setting:                The C++ API.         (line 355)
* operator bool () on Setting:           The C++ API.         (line 223)
* operator const char * () on Setting:   The C++ API.         (line 232)
* operator double () on Setting:         The C++ API.         (line 231)
* operator float () on Setting:          The C++ API.         (line 230)
* operator int () on Setting:            The C++ API.         (line 224)
* operator long () on Setting:           The C++ API.         (line 226)
* operator long long () on Setting:      The C++ API.         (line 228)
* operator std::string () on Setting:    The C++ API.         (line 233)
* operator unsigned int () on Setting:   The C++ API.         (line 225)
* operator unsigned long () on Setting:  The C++ API.         (line 227)
* operator unsigned long long () on Setting: The C++ API.     (line 229)
* operator= on Setting:                  The C++ API.         (line 308)
* operator[] on Setting:                 The C++ API.         (line 333)
* read on Config:                        The C++ API.         (line  48)
* readFile on Config:                    The C++ API.         (line  56)
* readString on Config:                  The C++ API.         (line  67)
* remove on Setting:                     The C++ API.         (line 458)
* setAutoConvert on Config:              The C++ API.         (line 101)
* setDefaultFormat on Config:            The C++ API.         (line 117)
* setFormat on Setting:                  The C++ API.         (line 518)
* setIncludeDir on Config:               The C++ API.         (line  84)
* setTabWidth on Config:                 The C++ API.         (line 126)
* write on Config:                       The C++ API.         (line  49)
* writeFile on Config:                   The C++ API.         (line  57)
* ~Config on Config:                     The C++ API.         (line  44)


File: libconfig.info,  Node: Type Index,  Next: Concept Index,  Prev: Function Index,  Up: Top

Type Index
**********

[index]
* Menu:

* Config:                                The C++ API.         (line   6)
* config_error_t:                        The C API.           (line  79)
* config_setting_t:                      The C API.           (line   6)
* config_t:                              The C API.           (line   6)
* ConfigException:                       The C++ API.         (line  13)
* FileIOException:                       The C++ API.         (line  27)
* ParseException:                        The C++ API.         (line  24)
* Setting:                               The C++ API.         (line   6)
* Setting::Format:                       The C++ API.         (line 520)
* Setting::Type:                         The C++ API.         (line 510)
* SettingException:                      The C++ API.         (line  30)
* SettingFormat:                         The C API.           (line 250)
* SettingNameException:                  The C++ API.         (line  21)
* SettingNotFoundException:              The C++ API.         (line  19)
* SettingTypeException:                  The C++ API.         (line  16)


File: libconfig.info,  Node: Concept Index,  Prev: Type Index,  Up: Top

Concept Index
*************

[index]
* Menu:

* aggregate value:                       The C API.           (line 421)
* array:                                 Configuration Files. (line  24)
* comment:                               Comments.            (line   6)
* configuration:                         Configuration Files. (line  24)
* escape sequence:                       String Values.       (line   6)
* format:                                The C API.           (line 250)
* group:                                 Configuration Files. (line  24)
* include directive:                     Include Directives.  (line   6)
* list:                                  Configuration Files. (line  24)
* locale:                                Internationalization Issues.
                                                              (line  14)
* path:                                  Configuration Files. (line  77)
* scalar value:                          Configuration Files. (line  24)
* setting:                               Configuration Files. (line  24)
* Unicode:                               Internationalization Issues.
                                                              (line   6)
* UTF-8:                                 Internationalization Issues.
                                                              (line   6)
* value:                                 Configuration Files. (line  24)



Tag Table:
Node: Top245
Node: Introduction532
Node: Why Another Configuration File Library?1368
Node: Using the Library from a C Program2444
Node: Using the Library from a C++ Program2912
Node: Multithreading Issues3577
Node: Internationalization Issues5144
Node: Compiling Using pkg-config6667
Node: Version Test Macros8197
Node: Configuration Files9383
Node: Settings13232
Node: Groups13550
Node: Arrays13824
Node: Lists14096
Node: Integer Values14382
Node: 64-bit Integer Values14846
Node: Floating Point Values15225
Node: Boolean Values15682
Node: String Values15954
Node: Comments17074
Node: Include Directives17981
Node: The C API19454
Node: The C++ API41050
Node: Example Programs65375
Node: Configuration File Grammar66483
Node: License67822
Node: Function Index95916
Node: Type Index106208
Node: Concept Index107446

End Tag Table