Configuration file format in MRPT

Configuration ("INI"-like) file format in MRPT.

Description

Plain text configuration files in MRPT follows a custom version of the INI file standard format, comprising "sections", "properties" (or "keys") with associated "values" and, optionally, comments.

The following C++ classes are provided to read and write such files:

• mrpt::config::CConfigFile: Access to physical files.
• mrpt::config::CConfigFileMemory: Wrapper around a configuration file "in memory", without an associated physical file.

See also:

• mrpt::config::CConfigFileBase: The base, virtual class underlying the two classes above. Users normally inkove the API exposed in this base class.
• mrpt::config::CConfigFilePrefixer: A proxy class to manipulate an object of the two classes above such that all accesses to sections and/or properties are mapped* to modified versions of their names.

Format specifications

• There exists only one level of hierarchy, i.e. only "toplevel" sections exist, there is no support for nested sections. A possible workaround to this limitation is using mrpt::config::CConfigFilePrefixer.
• Sections are formatted like: [section_name]
• Key/values pair follow the format: key = value. Whitespaces are ignored before and after the = sign, up to the first non-blank character of the value.
• API methods exist to read and write different elementary data types (int,double,std::string) and also vectors, matrices and even enums.
• Comments can be included in different formats:
  • Lines starting with ;. Example: ; Comment line
  • Lines starting with #. Example: # Comment line
  • After a value, with //. Example: key = value // Explanation of this value
  • An exception to the rule above is hard-coded to allow URLs, e.g. key = http://www.google.com is not considered to contain a comment.
• Preprocessor:
  • Just like in C/C++, lines can be ended in a backslash (\) to mean "line continuation". [New in MRPT 1.5.0]
  • C preprocessor-like #defines are available as @define VARNAME VALUE, then using variables as ${VARNAME} or math expressions as $eval{...}. See the example below: [New in MRPT 1.5.0].

    @define MAXSPEED 10
    @define MAXDIST  $eval{exp(2*MAXSPEED)}
    [test]
    var1=${MAXSPEED}
    var2=$eval{1+2*MAXSPEED}
    var3=$env{MY_ENV_VARIABLE}

Examples

There are dozens of examples in the subdirectory MRPT/share/mrpt/config_files.