Aargh

Automated Argument Helper

Summary

Synopsis

aargh [-l language] [-v] [-x ext] [-X hdr_ext] [filename]

The -v option requests verbose mode, in which aargh writes a serious of informational messages to standard output.

The -x option specifies the file name extension to be applied to the generated source code file, if not specified in the XML input file. If not specified in the XML input file nor on the aargh command line, the file name extension defaults to "c" for C and "C" for C++.

The -X option is similar to the -x option, except that it applies to the file name of the generated header. The file name extension for the header defaults to "h" if not otherwise specified.

The filename argument specifies an XML file defining the options that you want your program to support. If you don't specify an input file, aargh reads standard input.

Introduction

Not that it's difficult. It's just tedious, time-consuming, error prone, and no fun. I used to wince at the thought of adding command line options.

Not any more. All I have to do is define the options I want in a small XML file and run it through aargh. Instantly I have C or C++ source code that I can compile and link into my program. If I want to add another option or otherwise change the rules, I can edit the XML and regenerate the code. Now I can spend more time on the interesting parts of the project.

You can download aargh in the form of C++ source code and compile it yourself. It is licensed under the GNU General Public License (GPL).

Using Aargh

One file is a header that declares a C struct or a C++ class to represent the options. By default this struct or class is named "Opts," but you can specify a different name. The other file is the implementation of Opts (or whatever you decide to call it), providing a function to parse the command line. For C, the results are available as members of the struct. For C++, member functions perform the parsing and make the results available.

In your own code, declare an instance of Opts and call the parsing function, passing it the argc and argv arguments from main(). The parsing function returns zero if the command line follows the rules that you have outlined in the XML file, or non-zero otherwise. If the parsing is successful, the Opts object stores the results.

This process is easier to visualize with a simple example. A full example demonstrates all the available features in greater detail.

What You Can and Can't Do With Aargh

• You can enforce upper and/or lower limits on the number of non-option arguments.
• You can distinguish between options that take arguments and those that don't.
• You can specify that an option is required.
• You can require that the argument to an option be a non-negative integer.
• For an integer argument you can enforce upper and/or lower limits.
• For a string argument you can enforce upper and/or lower limits on the string length.
• For a string argument you can call a function of your own to validate the argument.
• For a string argument you can specify a default value to be applied when the option is omitted.
• By default the generated software allows only one occurrence of any given option, but you can allow multiple occurrences. In that case the generated code stores the arguments in a linked list (for C) or an STL vector (for C++).
• You can add customized comments to a comment block at the top of the generated source files.

There are other situations that aargh can't handle:

• You can't define an option that sometimes takes an argument and sometimes doesn't.
• You can't keep track of the order in which the options occur.
• You can't generate code for any language other than C or C++. Support for other languages wouldn't be hard to add, just tedious.
• You can't validate interactions among different options. For instance, you can't specify that the -t and -v options are incompatible, or that the presence of a -i option requires that there be a -o option as well. You can still enforce those kinds of rules outside of the generated code.

• Forget about aargh and write your own code from scratch.
• Take the code generated by aargh and modify it.
• Modify aargh to extend its power. If you do, I hope you will share your enhancements with the world, as permitted (and encouraged) by the GPL.

Licensing

This license does not extend to the code generated by aargh, which belongs to whoever generates it. I claim no rights to the code you generate. You can license it under whatever terms you choose, or not license it at all.

Acknowledgements

Scott McKellar