CommandExecutor.java

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;

public class CommandExecutor
{
    /**
     * Run single, external script, program, system command, etc.
     * @author: richarduie [at] yahoo [dot] com
     *
     * Usage syntax is static call to main as:
     *    CommandExecutor cmd
     *      run command and ignore output of external command process
     *    CommandExecutor cmd true
     *      run command and capture output of external command process for
     *      display in output stream of current process
     *
     * args[0] - command to execute
     * args[1] - optional flag (true/<anything else> to indicate whether
     *           to capture command output and display in ouput stream
     *           for current process
     *
     * NOTE: if command (args[0]) includes spaces, it must be in quotes, e.g.,
     *       [CommandExecutor "ls /" true] lists all subdirectories from root
     *       of a *nix installation and writes output to current stream
     */

    public static void main(String[] args) {
        // report usage error and exit, if no arguments
        if (0 == args.length) {
            System.out.println("CommandExecutor.main() - no command given");
            return;
        }
        // if second argument given and value is String "true", capture
        // output from external command output stream and write to output
        // stream for this process
        boolean capture = 1 < args.length && "true".equals( args[1] );
        try {
            // execute command - will run in separate, external
            // process not directly impacting current console
            Process p = Runtime.getRuntime().exec( args[0] );
            // retrieve and display output stream of command process
            if (capture) {
                // for read/write of stdout for command process
                String str;
                // read in process output associated with command
                BufferedReader in = new BufferedReader(
                    new InputStreamReader( p.getInputStream( ) )
                );
                // write each line of external command process to
                // current console
                while ( null != (str = in.readLine( ))) {
                    System.out.println( str );
                }
            }
        }
        catch (IOException e) {
            System.out.println(
                "CommandExecutor.main() - could not run command:\n" +
                args[0] + "\nException reported was:\n" + e.toString()
            );
        }
    }
}