Example: Use input and output streams for interprocess communication

In this example, the C program writes a string to its standard output stream, and the Java program reads this string and displays it. This example assumes that a library, which is named JAVSAMPLIB, has been created and that the CSAMP1 program has been created in it.

Example 1: CallPgm class

import java.io.*;
 
public class CallPgm
{
   public static void main(String args[])
   {
      Process theProcess = null;
      BufferedReader inStream = null;
 
      System.out.println("CallPgm.main() invoked");
 
      // call the CSAMP1 program
      try
      {
          theProcess = Runtime.getRuntime().exec(
                       "/QSYS.LIB/JAVSAMPLIB.LIB/CSAMP1.PGM");
      }
      catch(IOException e)
      {
         System.err.println("Error on exec() method");
         e.printStackTrace();  
      }
 
      // read from the called program's standard output stream
      try
      {
         inStream = new BufferedReader(new InputStreamReader
                           (theProcess.getInputStream()));
         System.out.println(inStream.readLine());
      }
      catch(IOException e)
      {
         System.err.println("Error on inStream.readLine()");
         e.printStackTrace();  
      }
 
   } // end method
 
 } // end class

Example 2: CSAMP1 C Program

#include <stdio.h>
#include <stdlib.h>
 
void main(int argc, char* args[])
{
     /* Convert the string to ASCII at compile time */
#pragma convert(819)
     printf("Program JAVSAMPLIB/CSAMP1 was invoked\n");
#pragma convert(0)
     /* Stdout may be buffered, so flush the buffer */
 
     fflush(stdout);
 
}

For more information, see Use input and output streams for interprocess communication.