source: gli/branches/rtl-gli/src/org/greenstone/gatherer/util/ExternalProgram.java@ 18353

package org.greenstone.gatherer.util;


import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.OutputStreamWriter;
import org.greenstone.gatherer.DebugStream;


/**
 * This class provides a convenient method of running external programs and viewing/analysing
 * their output. The external programs may be run with or without arguments. 
 */
public class ExternalProgram
{
    private Process programProcess = null;

    private BufferedReader programOut = null;
    private BufferedReader programErr = null;


    /**
     * Prepares to run a specified external program with the specified arguments.
     *
     * @param programName The name (and path, if necessary) of the program to run.
     * @param programArgs The arguments to provide to the program when run.
     */
    public ExternalProgram(String programName, String programArgs)
    throws IOException
    {
    // Run the program
    programProcess = Runtime.getRuntime().exec(programName + " " + programArgs);

    // Grab the program output
    programOut = new BufferedReader(new InputStreamReader(programProcess.getInputStream()));
    programErr = new BufferedReader(new InputStreamReader(programProcess.getErrorStream()));

    }



    /**
     */
    public int exitProgram()
    throws IOException
    {
    // Finished, thank you
    //programIn.close();

    // Wait for the process to finish
    try {
        programProcess.waitFor();
    }
    catch (InterruptedException ex) {
        throw new Error("Internal Error: Process interrupted.\n" + ex);
    }

    // Return the program exit value
    return programProcess.exitValue();
    }


    /**
     * Returns a single line of output sent by the program to standard output.
     *
     * @return a single line of output sent by the program to standard output.
     */
    public String getLineOfProgramOutput()
    {
    // Read in a line from the program output
    try {
        if (programOut.ready())
        return programOut.readLine();
        else
        return null;
    }
    catch (IOException ex) {
        DebugStream.println("Error: Exception occurred while reading program output.");
        DebugStream.println("Exception: " + ex);
        return null;
    }
    }


    /**
     * Returns a single line of output sent by the program to standard error.
     *
     * @return a single line of output sent by the program to standard error.
     */
    public String getLineOfProgramError()
    {
    // Read in a line from the program error
    try {
        if (programErr.ready())
        return programErr.readLine();
        else
        return null;
    }
    catch (IOException ex) {
        DebugStream.println("Error: Exception occurred while reading program error.");
        DebugStream.println("Exception: " + ex);
        return null;
    }
    }
}