Runtime.getRuntime() help plzzzzzzzz

[nana Amr]

hi all,,
im working at a project which must: take student homework then check if the homework is correct or not
ex: student homework saved on a file name "hwfile.java" so my program will
compile and then run this file and get the output,, then compair this output with the correct answer(correct answer entered by techer and saved on text file...)
my problem is how to use Runtime.getRuntime().exec(...) to combile and run a file???
what is the parameter will be " Runtime.getRuntime().exec(???) " ??
HELP

[Sanju Thomas]

The parameter to the exec should be the command that has to be executed, in your case you must give "javac to compile and java to execute".

Process p = Runtime.getRuntime().exec("javac Test.java");

Then you can use any one of these methods of process class, depends of your need, getInputStream will return the result of the executed process.

public abstract java.io.InputStream getErrorStream();
public abstract java.io.InputStream getInputStream();
public abstract java.io.OutputStream getOutputStream();

[Ernest Friedman-Hill]

Moving to JiG Intermediate.

[nana Amr]

Sanju Thomas
thax alot for ur reply,,,
but plz tell me should i determain the bath where the javac is?? like if we trying to combile or run at cmd?

and if the file.cpp what is the parameter be??
plz answer me and thx alot again
[ May 18, 2005: Message edited by: nana mm ]

[Sanju Thomas]

I did not understand your question.

[nana Amr]

i try what u told me, its compile the file put i dont know how to get the output using the methods u write

and if the file is a c++ file (file.cpp) what the parametr should be in
.exec(?? file.cpp) if u know tell me plz

[nana Amr]

can you plz explain me how to use this:
public abstract java.io.InputStream getErrorStream();
public abstract java.io.InputStream getInputStream();
public abstract java.io.OutputStream getOutputStream();

[Sanju Thomas]

Suppose that you need to compile this program

 
class Test{
public static void main(String args[]){
System.out.println("test";
}
} 

This program have an error, you must have seen println is not closed.

Now how we can compile this program and get the errorStream ?

 
import java.io.InputStream;
import java.io.OutputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
 

public class PP{
public static void main(String args[])throws Exception{
Process p = Runtime.getRuntime().exec("javac Test.java");
InputStream ip = p.getErrorStream();
        InputStreamReader inputstreamreader =    new InputStreamReader(ip);
                BufferedReader bufferedreader =  new BufferedReader(inputstreamreader);    
                String line = null;
System.out.println(bufferedreader.readLine());
            while ((line = bufferedreader.readLine()) 
                      != null) {
                System.out.println(line);
            }

}
}

See the output

C:\work\java>java PP
Test.java:6: ')' expected
System.out.println("test";
^
1 error

In this way you can get the ErrorStream, InputStream and OutputStream.
Sorry for the late replay, I was bit busy.

[Sanju Thomas]

To compile c++ or any other program you need to use the required compiler. I think gcc is used to compile c++ program.

Runtime.getRuntime().exec("gcc test.cpp");

gcc must be available in the system path.

[Sanju Thomas]

To run the java program

 
Runtime.getRuntime().exec("java Test");
InputStream ip = p.getInputStream();
InputStreamReader inputstreamreader =    new InputStreamReader(ip);
BufferedReader bufferedreader =  new BufferedReader(inputstreamreader);
String line = null;
System.out.println(bufferedreader.readLine());
while ((line = bufferedreader.readLine()) != null) {
                System.out.println(line);
}

The result will be
C:\work\java>java PP
test

[nana Amr]

i will try this thanx alot for ur help

[nana Amr]

but what if i need to pass a value to the other program like if :

 
import java.io.*;
public class test
{
public static void main(String args[])
{
int a=0;int b=0;
 
System.out.print("enter avalue1\n");
 
InputStream input =System.in;
InputStreamReader reader=new InputStreamReader(input);
try{
BufferedReader buff=new BufferedReader(reader);
 
String value=buff.readLine();
a=Integer.parseInt(value);
 
System.out.print("enter avalue2\n");
        value=buff.readLine();
b=Integer.parseInt(value);
 
System.out.print(a+b);
}catch(IOException ioe){}
}
}
 

how can i run it?

[Sanju Thomas]

Then you need to use the getOutputStream()

[nana Amr]

im sorry i asked to much but
can i pass the arguments in someway like:
Process pr=Runtime.getRuntime().exec("java test 10 20");
and the a=args[0]; b= args[1]?? or it done in diffrent way
[ May 19, 2005: Message edited by: nana mm ]

[nana Amr]

and if the arguments are variables??

[Rene Larsen]

and if the arguments are variables??

one way is like this:

Process pr=Runtime.getRuntime().exec("java test " + a + " " + b);

Rene

[nana Amr]

Rene,,
i try what u say and its work thx alot

[nana Amr]

i need to execute a file which is in a diffrent path i try this:

 Process p = Runtime.getRuntime().exec("javac D:/files/Gproject/test.java");
 

but it dose not work
then i try this:

 
String file="D:/files/Gproject/test.java";
Process p = Runtime.getRuntime().exec("javac "+file);
 

and not work too??
plz tell me what to do

[Rene Larsen]

What are the errors you are getting?

If you type 'javac' in a Command prompt you'll see the options you can set on 'javac'

e.g. javac -sourcepath D:/files/Gproject Test.java

Rene
[ May 22, 2005: Message edited by: Rene Larsen ]

[nana Amr]

can i use this:

Process pr=Runtime.getRuntime().exec("javac -sourcepath D:/files/Gproject Test.java
);
  

??

[Rene Larsen]

I'll say yes.

Have you tried it?

PS.: Just remember that your java class name is with lowercase.

Rene

[nana Amr]

i can run the program coz i dont know how to pass the directory:

String dir="D:/files/Gproject/";
String fileName="test"; 
String arg1="10";  
String arg2="20";
Process pr=Runtime.getRuntime().exec("java  "+dir+" "+fileName+" "+arg1+" "+arg2);
  

but it not work and i dont know what to do??

[nana Amr]

plz help me i dont know what to do

[Sanju Thomas]

If its windows, then you can use this code.

  
 
Process p = Runtime.getRuntime().exec("javac c:\\work\\java\\Test.java");
InputStream ip = p.getErrorStream();
        InputStreamReader inputstreamreader = new InputStreamReader(ip);
                BufferedReader bufferedreader =  new BufferedReader(inputstreamreader);     
                String line = null;
 
            while ((line = bufferedreader.readLine()) 
                      != null) {
                System.out.println(line);
            }
 

[nana Amr]

its work
thaxxxxxxxxxx alot

[Arjun K]

If you are working on j2se 5.0 then you can use processbuilder to run a process.
http://java.sun.com/j2se/1.5.0/docs/api/java/lang/ProcessBuilder.html

Process prs1 = new ProcessBuilder("ps", "-aef").start();
//Here below the error and output stream will be directed to a comman stream
ProcessBuilder pb2 = new ProcessBuilder("javac", " c:\\work\\java\\Test.java").redirectErrorStream(true); 
try{
   Process p2 = pb2.start();
   BufferedReader br1 = new BufferedReader(new InputStreamReader(p2.getInputStream()));
   String line = null;
   while((line=br1.readLine())!=null); 
System.out.println(line);
}catch(Exception e) {
   e.printStackTrace();
}
}
 
Hope this helps,
Arjun