Jakarta Commons Cookbook

7.2. Parsing a Simple Command Line

Problem

You need to parse a simple command line containing optional and required arguments.

Solution

Use the Jakarta Commons CLI to parse program arguments. Populate an Options object to configure command-line parsing. Pass the Options class and a String[] of arguments to a CommandLineParser, which parses and returns a CommandLine object capturing the supplied options and parameters.

For the purposes of this recipe, assume that you are attempting to parse a command line with three optional arguments: -h, -v, and -f <filename>. -h prints out a simple help message with usage information and available command-line options, -v runs the program with verbose logging, and -f sends the output of the application to a file. To parse this command line, your main( ) method would resemble the following code:

               import org.apache.commons.cli.CommandLineParser;
               import org.apache.commons.cli.BasicParser;
               import org.apache.commons.cli.Options;
               import org.apache.commons.cli.CommandLine;

               public static void main(String[] args) throws Exception {

    // Create a Parser
    CommandLineParser parser = new BasicParser( );
    Options options = new Options( );
    options.addOption("h", "help", false, "Print this usage information");
    options.addOption("v", "verbose", false, "Print out VERBOSE information" );
    options.addOption("f", "file", true, "File to save program output to"); // Parse the program arguments CommandLine commandLine = parser.parse( options, args ); // Set the appropriate variables ...