Introduction

The utilities in org.apache.avalon.excalibur.cli assist you in parsing command line options during startup time. It allows you to associate a short option and a long option to the same command, and then test for it in a switch statement.

Usage Example

import java.util.List;

import org.apache.avalon.excalibur.cli.CLArgsParser;
import org.apache.avalon.excalibur.cli.CLOption;
import org.apache.avalon.excalibur.cli.CLOptionDescriptor;
import org.apache.avalon.excalibur.cli.CLUtil;

/**
* Demonstrates the excalibur command-line parsing utility.
*
* @author Jeff Turner
*/
public class CLDemo {
    // Define our short one-letter option identifiers.
    protected static final int HELP_OPT = 'h';
    protected static final int VERSION_OPT = 'v';
    protected static final int MSG_OPT = 'm';

    /**
     *  Define the understood options. Each CLOptionDescriptor contains:
     * - The "long" version of the option. Eg, "help" means that "--help" will
     * be recognised. 
     * - The option flags, governing the option's argument(s).
     * - The "short" version of the option. Eg, 'h' means that "-h" will be
     * recognised.
     * - A description of the option.
     */
    protected static final CLOptionDescriptor [] options = new CLOptionDescriptor [] {
        new CLOptionDescriptor("help",
                CLOptionDescriptor.ARGUMENT_DISALLOWED,
                HELP_OPT,
                "print this message and exit"),
        new CLOptionDescriptor("version",
                CLOptionDescriptor.ARGUMENT_DISALLOWED,
                VERSION_OPT,
                "print the version information and exit"),
        new CLOptionDescriptor("msg",
                CLOptionDescriptor.ARGUMENT_REQUIRED,
                MSG_OPT,
                "the message to print"),
    };

    public static void main(String args[]) {
        // Parse the arguments
        CLArgsParser parser = new CLArgsParser(args, options);

        if( null != parser.getErrorString() ) {
           System.err.println( "Error: " + parser.getErrorString() );
           return;
        }

        // Get a list of parsed options
        List clOptions = parser.getArguments();
        int size = clOptions.size();

        for (int i = 0; i < size; i++) {
            CLOption option = (CLOption) clOptions.get(i);

            switch (option.getId()) {
                case CLOption.TEXT_ARGUMENT:
                    System.out.println("Unknown arg: "+option.getArgument());
                    break;

                case HELP_OPT:
                    printUsage();
                    break;

                case VERSION_OPT:
                    printVersion();
                    break;


                case MSG_OPT:
                    System.out.println(option.getArgument());
                    break;
            }
        }
    }

    private static void printVersion() {
        System.out.println("1.0");
        System.exit(0);
    }

    private static void printUsage() {
        String lSep = System.getProperty("line.separator");
        StringBuffer msg = new StringBuffer();
        msg.append("------------------------------------------------------------------------ ").append(lSep);
        msg.append("Excalibur command-line arg parser demo").append(lSep);
        msg.append("Usage: java "+CLDemo.class.getName()+" [options]").append(lSep).append(lSep);
        msg.append("Options: ").append(lSep);
        msg.append(CLUtil.describeOptions(CLDemo.options).toString());
        System.out.println(msg.toString());
        System.exit(0);
    }
}