hleclerc / PrepArg

A simple and "agnostic" C/C++ argument parser

What is PrepArg ?

PrepArg is a simple and agnostic argument parser for C and C++, based primarily on preprocessor directives. Thus:

• it does not allocate any dynamic memory;
• it does not depend on any specific library;
• it is highly configurable.

It follows the GNU conventions.

Following the DRY (Don't Repeat Yourself) principles, things are specified once (as much as possible).

A simple example

Declarations

Arguments must by defined in a separate file, containing declarations like:

DESCRIPTION( "test prg" );

SARG( 's', my_string , "A string" , "default value" );
BARG( 'b', my_boolean, "A boolean", false );
EARG( an_integer, "help message" );

SARG means string argument (by default a const char *).

BARG means boolean argument (a flag).

IARG means integer argument (with corresponding checks).

DARG means floating point argument (double by default, with corresponding checks).

EARG means final argument. If used, it is an integer (-1 by default) that describes the first non managed argument.

Arguments of SARG(), BARG(), ... are:

• char for single letter options (-s, -b, ...). as specified by the gnu conventions, multiple options (specified with the single char versions) may follow a hyphen delimiter in a single token if the options do not take arguments. Thus, ‘-abc’ is equivalent to ‘-a -b -c’.
• variable name. This value is also used for long options, but '_' are replace by '-'. In this example, PrepArg will look for '--my-string' and '--my-boolean'
• argument description. Used by the usage function.
• default value.

Use

To use these declarations, you have to #define a macro containing the name of this file and #include the PrepArg files to get the corresponding functionnalities, as in:

// path of the aformentionned file
#define PREPARG_FILE "../my_args.h"

// will include the "generated" usage function (and some helpers for parse)
#include <PrepArg/usage.h>

int main( int argc, char **argv ) {
    // will include the variables declaraction (my_string, my_boolean, ...) with their default values
    #include <PrepArg/declarations.h>

    // for loop that will parse the arguments of main
    #include <PrepArg/parse.h>

    // helper that will display the arguments names, and their values (e.g. for a verbose mode)
    #include <PrepArg/info.h>

    // obviously, results can be used directly
    int foo = 2 * my_boolean;
}

Configuration

Configuration may be done using #define. Main options are defined in src/PrepArg/default_values.h.

For example, if const char * is to be replaced by std::string, one can write something like

#define PREPARG_S( A ) std::string A
#include <PrepArg/usage.h>

int main( int argc, char **argv ) {
    ...
}

Some configurations issues can also be managed using specific .h files, as e.g. in test_class.cpp which illustrates how to store the variables as class attributes.

And now ?

This code is under the LGPLv3 license.

New functionnalities are very welcome !