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Thread: Why runtime error?

  1. #1
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    Default Why runtime error?

    Hello.
    I get a run-time error executing my code. Can anyone tell me why?

    Thanks in advance

    Here is my class with main():
    class ExecDemo{
    	   // Date	d = new Date();
     
    	   public static void main( String args[] ){
    	   Runtime r = Runtime.getRuntime();
    	   Process p = null;
     
    	    try{
    		   p = r.exec("ls");
    		   p.waitFor();
    	       p=r.exec("ping 8.8.8.8");
    	   }
    	   catch(Exception e){
    		   System.out.println("Error executing ps");
    	   }//end try..catch block
    	   System.out.println("ps returned " + p.exitValue());	
    	   System.out.println("Total Memory is: " + r.totalMemory());
    	   System.out.println("Total Memory is: " + System.getProperty("CPU"));
     
    	}//end main( string args[] )
    }


  2. #2
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Why runtime error?

    Can you tell us what the error is?
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    Default Re: Why runtime error?

    This is my screen output:

    soheil@soheil-desktop:~/test_suite$ java ExecDemo
    Exception in thread "main" java.lang.IllegalThreadStateException: process hasn't exited
    at java.lang.UNIXProcess.exitValue(UNIXProcess.java:1 88)
    at ExecDemo.main(ExecDemo.java:25)
    soheil@soheil-desktop:~/test_suite$

  4. #4
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Why runtime error?

    That error tells you that the Process hasn't exited. Your code waits for the first process to exit, but not the second one.
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  5. The Following User Says Thank You to KevinWorkman For This Useful Post:

    hooshdar3 (March 12th, 2014)

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    Default Re: Why runtime error?

    I called waitFor() for the 2nd instance of the process, but nothing appeared at the output.
    Similar;y, I wrote:
    p = r.exec("top -n1");
    p.waitFor();
    again, with no result whatsoever.

  7. #6
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Why runtime error?

    What output are you expecting?
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    Default Re: Why runtime error?

    Quote Originally Posted by KevinWorkman View Post
    What output are you expecting?
    I expect the same output as when exdecuting free-m or top -n1 from the command prompt/terminal

    --- Update ---

    I look for a call similar to C++ system(), most efficient.

  9. #8
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Why runtime error?

    I would use a ProcessBuilder if I were you.

    And you need to separate your arguments. Instead of exec("top -n1") it would be exec("top", "-n1");
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    Default Re: Why runtime error?

    exec("top", "-n1"); errors at compile time

  11. #10
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Why runtime error?

    Again, what is the error? Have you tried using a ProcessBuilder?
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    Default Re: Why runtime error?

    This is the only info I get:

    ExecDemo.java:20: cannot find symbol
    symbol : method exec(java.lang.String,java.lang.String)
    location: class java.lang.Runtime
    p = r.exec("top" , "-n1");
    ^
    1 error
    soheil@soheil-desktop:~/test_suite$

    --- Update ---

    I need to obtain the memory status + CPU speed

  13. #12
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    Default Re: Why runtime error?

    The error message in your last post is simply stating that the Runtime class doesn't have an exec() method with 2 String parameters. See Runtime (Java Platform SE 7 ) for the different variants of the exec() method.

    Alternatively, as KevinWorkman suggested, you can use ProcessBuilder to do this. See ProcessBuilder (Java Platform SE 7 ).

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