RConfig

mylib/trunk/rconfig

A readable config file (rcfile) parser and variable binder. This is totally sexy, if I can say that. The goal of this guy was to make it easy to initialise variables already declared in the normal course of programming, by getting values from a config file (or the environment) in as few lines as possible. After many iterations, this is now down to an additional 0 lines of code. Yes, zero. Time for a use-case.

Use Cases

Imagine, in the course of programming some application, you defined a variable as follows:

int myint = 5;

Now, you want to allow users to override myint in a configuration file, or by running your application as:

$ myint=5 ./myapp

Enter RConfig. Just change the definition to

int RCFILE_CONFIGVAR(myint, 5);

And you're done! Well. almost. You also need to actually parse the file at some point. So let's do a more complete example.

Hello World

Here is a complete "Hello World" main.cpp:

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

std::string RCFILE_CONFIGVAR(world, "world!");

int main() {
  RConfig::rcfile_parse("config.txt");
  std::cout << "Hello " << world << std::endl;
  return 0;
}

Now what happens when we run it:

$ ./hello_world 
(cfg) std::string     world                          = world!               (hello_world.cpp)
Hello world!

$ world="Environment" ./hello_world 
(cfg) std::string     world                          = world!               (hello_world.cpp)
Overriding default world to Environment
Hello Environment

$ echo "world = configfile" > config.txt
$ ./hello_world 
(cfg) std::string     world                          = world!               (hello_world.cpp)
Overriding default world to configfile
Hello configfile

0 lines??

So why is this "0 lines". Well, for each extra variable you add, you only need to tweak the line that declares the variable. Hence, 0 lines are added. Also, the fact that this is a variable parsed from the config file becomes part of the declaration -- this is great intrinsic documentation!

More features

The examples above show an integer and std::strings. All primitive types are supported, and std::string, and std::vectors of any of these (each time a value for a vector is found, it just gets pushed back, rather than replaced.

More examples

Have a look at the "configapp" in mylib/trunk/configapp. The hello world use case can also be found at mylib/trunk/rconfig/hello_world.cpp

Documentation

Not generated yet, but it should eventually appear at (Doxygen index)

Requirements

• cmake http://www.cmake.org/

• Regular expressions -- either Boost or my own RxString

SVN Checkout & Building & Running

See also ConfigApp? (part of mylib?)

svn co http://code.apted.net/svn/pub/mylib/trunk/rconfig
(cd rconfig && svn export http://code.apted.net/svn/pub/cmake/SuggestCXXFlag.cmake)
mkdir rconfig-build && cd rconfig-build
cmake ../rconfig && make
./hello_world