S.O.S PROBLEMS COMUNICATING EXTERNAL PROCESES IN JAVA UNDER LINUX

Question

I've programmed a little program in C called "cinterpreter" which works like
an interpreter, when it launches it shows a welcome message to the display
(standart output), then is always waiting for strings from the keyboard
showing the length of the input strings until the "quit" string is received,
in that case the C program named "cinterpreter" finish, here we can see the
code:
# include <stdio.h>
# include <string.h>
# include <stdlib.h>
char presentacion[8][80] = {
" ||||||||||||||||||\n",
" --- Welcome to Maude ---\n",
" ||||||||||||||||||\n",
" Maude version 1.0.5 built: Apr 5 2000 15:56:52\n",
" Copyright 1997-2000 SRI International\n",
" Thu Aug 9 13:40:25 2001\n",
" \n",
" \n"};
void longitud(char * cadena)
int t;
for(t=0;t<3;t++)
printf("MAUDE_OUT> la cadena %s tiene %d caracteres\n",cadena,strlen(cadena));
fflush(stdout);
int main()
char cadena[80];
int i;
char ch;
for(i=0;i<8;++i) printf("%s",presentacion);
printf("\n");
fflush(stdout);
do {
printf("Press any key to continue\n");
scanf("%c",&ch);
printf("%c\n",ch);
fflush(stdout);
}while (ch != 'q');
printf("\n");
while( strcmp(cadena,"quit") !=0)
printf("\nMAUDEENTRADA>");
fflush(stdout);
scanf("%s",cadena);
longitud(cadena);
I'm intereted in running this program, control it's standart input and
starndart output through a java program through the Runtime , process class
and the correponding methods like "exec", getInputStream, getOutputStream,
getErrorStream, the question is that I do not Know what I'm doing wrongly but
I don't get what I want, I'm interested in sending input to the C subprocess
thorugh its stdin getting it by getoutputStream method, and then read its
answer from its stdout getting it by getoutputStream, then question is that I
can sent de first string and read the first answer but I can't repeat it
again, and I would like to begin a dialog with the subprocess so I need to
send many messages and receive its answer to it, but many times, not just one,
by the moment I got it but just one, it's very important that it's necesary to
to interact with the subprocess like:
1) send first string and then read the answer of the subprocess
2) send the second string and then read the answer
these steps must be done all the times I want, but I just can send the first
string and read the first answer but no more steps work well, if any body can
help with this please
answer the question or send any answer to the next adresses
e-mail:
[email protected]
[email protected]
*************** java code **********************
import java.io.*;
public class mioss {
static String proceso = "/bin/cinterprete";
static Process p = null;
//--------- input writting method -----------
static void escribe(OutputStream procesoescribe, String s) {
BufferedWriter laentrada = new BufferedWriter(new
OutputStreamWriter(procesoescribe));
try{
laentrada.write(s + "\n");
laentrada.flush();
}catch(IOException e) {System.out.println("error de escritura");}
//----------- output reading method ---------------
static void leesalida(InputStream procesosalida){
String l;
BufferedReader lasalida = new BufferedReader(new
InputStreamReader(procesosalida));
try{
while ((l = lasalida.readLine()) != null){
System.out.println(l);
} catch(IOException e) {System.out.println("error de readline");}
//------------- reading error method --------------------
static void leerror(Process p){
String l;
BufferedReader elerror = new BufferedReader(new
InputStreamReader(p.getErrorStream()));
try{
while ((l = elerror.readLine()) != null){
System.out.println(l);
elerror.close();
} catch(IOException e) {System.out.println("error de readline");}
//--------------- principal method main -------------------------
static Process proc = null;
public static void main(String [] Args) {
try{
Runtime r = Runtime.getRuntime();
proc = r.exec(proceso);
escribe(proc.getOutputStream(),"map(+2)[3,3]");
leesalida(proc.getInputStream());
escribe (proc.getOutputStream(),"map(*3)[2,2]");
leesalida(proc.getInputStream());
}catch(Exception e) {System.out.println("error de ejecucion del
proceso");}
System.out.println("THE END OF THE PROGRAM");

Answer 1

Just a guess, but I think your problem is at least partly due to repeated getting the Input and Output Streams of the process and repeatedly wrapping them in Readers and Writers. Get the InputStream once and wrap it in a Reader once and use that Reader. Also get the OutputStream once and wrap it in a Writer once and use that Writer.