Class ExecRunner


  • public class ExecRunner
    extends Object

    Makes running external executables easier, optionally under a watched thread. In addition, probably the most useful feature of ExecRunner is using it to run a command-line program and obtain its stdout and stderr results in two strings. This is done with exec(String) - see that method for an example. With acknowledgements to Michael C. Daconta, author of "Java Pitfalls, Time Saving Solutions, and Workarounds to Improve Programs." and his article in JavaWorld "When Runtime.exec() Won't".

    Version:
    CVS $Id$
    Author:
    Scott McCrory., Francois Pepin, Andreas Dräger
    • Constructor Detail

      • ExecRunner

        public ExecRunner()
        Basic ExecRunner constructor.
      • ExecRunner

        public ExecRunner​(String command,
                          String[] arguments)
                   throws ExceptionInInitializerError
        ExecRunner constructor which also conveniently runs exec(String).
        Parameters:
        command - The program or command to run
        arguments - An array of Strings in which every single String is exactly one of the program's arguments. So these arguments are allowed to contain white spaces and are marked as Strings by the system.
        Throws:
        ExceptionInInitializerError - thrown if a problem occurs
        Since:
        1.5
    • Method Detail

      • exec

        public int exec​(String command)
                 throws IOException,
                        InterruptedException
        The exec(String) method runs a process inside of a watched thread. It returns the client's exit code and feeds its STDOUT and STDERR to ExecRunner's out and err strings, where you then use getOutString() and getErrString() to obtain these values. If the command String contains arguments which are Strings containing white spaces, the method
        exec(program, arguments)
        should be used instead, where arguments is a String[] array containing the arguments of the program. Example:
         // Execute the program and grab the results
         String out = "";
         String err = "";
         try {
        
             ExecRunner er = new ExecRunner();
             er.setMaxRunTimeSecs(maxRunTime);
             er.exec(program);
             if (!er.getMaxRunTimeExceeded()) {
                 out = er.getOutString();
                 err = er.getErrString();
             }
             else {
                 log.error("Maximum run time exceeded!");
                 continue;
             }
        
         }
         catch (Exception e) {
             log.error("Error executing " + program + ": " + e.getMessage());
             continue;
         }
         
        Parameters:
        command - The program or command to run
        Returns:
        The command's return code
        Throws:
        IOException - thrown if a problem occurs
        InterruptedException - thrown if a problem occurs
      • exec

        public int exec​(String command,
                        String[] arguments)
                 throws IOException,
                        InterruptedException
        Sometimes special cases may occur that the arguments of an external program are Strings containing white spaces. Another example are external processes needing the String arguments to be characterized in a special way. In this cases it is sensefull to write every single argument in an String array. The system itselfe will mark these arguments as Strings so that these special encoding can be omitted.
        Parameters:
        command - The external program to be executed.
        arguments - An array of Strings. Every entry of this array is an argument of the external program to be executed.
        Returns:
        The command's return code
        Throws:
        IOException - thrown if a problem occurs
        InterruptedException - thrown if a problem occurs
        Since:
        1.5
      • exec

        public int exec​(String command,
                        String[] arguments,
                        OutputStream stdoutStream,
                        OutputStream stderrStream)
                 throws IOException,
                        InterruptedException
        Convenience method for calling exec with OutputStreams.
        Parameters:
        command - The program or command to run
        arguments - An array of Strings containing the program's arguments.
        stdoutStream - java.io.OutputStream
        stderrStream - java.io.OutputStream
        Returns:
        The command's return code
        Throws:
        IOException - thrown if a problem occurs
        InterruptedException - thrown if a problem occurs
        Since:
        1.5
      • exec

        public int exec​(String command,
                        PrintWriter stdoutWriter,
                        PrintWriter stderrWriter)
                 throws IOException,
                        InterruptedException
        The exec(String, PrintWriter, PrintWriter) method runs a process inside of a watched thread. It returns the client's exit code and feeds its STDOUT and STDERR to the passed-in streams.
        Parameters:
        command - The program or command to run
        stdoutWriter - java.io.PrintWriter
        stderrWriter - java.io.PrintWriter
        Returns:
        The command's return code
        Throws:
        IOException - thrown if a problem occurs
        InterruptedException - thrown if a problem occurs
      • exec

        public int exec​(String command,
                        String[] arguments,
                        PrintWriter stdoutWriter,
                        PrintWriter stderrWriter)
                 throws IOException,
                        InterruptedException
        The exec(String, PrintWriter, PrintWriter) method runs a process inside of a watched thread. It returns the client's exit code and feeds its STDOUT and STDERR to the passed-in streams. The arguments for the external program or command are passed as an array of Strings. This has the advantage that the arguments are allowed to contain white spaces and are marked to be Strings by the System itselfe, which is sometimes important. Every single argument has to be exactly one dimension of the arguments array.
        Parameters:
        command - The program or command to run
        arguments - An array of Strings containing the program's arguments/options.
        stdoutWriter - java.io.PrintWriter
        stderrWriter - java.io.PrintWriter
        Returns:
        The command's return code
        Throws:
        IOException - thrown if a problem occurs
        InterruptedException - thrown if a problem occurs
        Since:
        1.5
      • getErrString

        public String getErrString()
        Returns the error string if exec(String) was invoked.
        Returns:
        The error string if exec(String) was invoked.
      • getMaxRunTimeExceeded

        public boolean getMaxRunTimeExceeded()
        Returns whether the maximum runtime was exceeded or not.
        Returns:
        boolean indicating whether the maximum runtime was exceeded or not.
      • getMaxRunTimeSecs

        public int getMaxRunTimeSecs()
        Returns the maximum run time in seconds for this object.
        Returns:
        the maximum run time in seconds for this object.
      • getOutString

        public String getOutString()
        Returns the output string if exec(String) was invoked.
        Returns:
        The output string if exec(String) was invoked.
      • main

        public static void main​(String[] args)
                         throws IOException
        This is for unit testing of the class.
        Parameters:
        args - an array of command-line arguments
        Throws:
        IOException - thrown if a problem occurs
      • setMaxRunTimeSecs

        public void setMaxRunTimeSecs​(int max)
        Sets the maximum run time in seconds. If you do not want to limit the executable's run time, simply pass in a 0 (which is also the default).
        Parameters:
        max - Maximim number of seconds to let program run