请教java与c++通过管道交互的问题

[duotiger]

c++里面fork，两个pipe，父进程把字符串写入pipe1[1]，并读取pipe2[0]；子进程重定向标准输入到pipe1[0]、标准输出到pipe2[1]，然后启动java。
java里面就是读一下标准输入，然后再输入一些字符串。
问题是：现在从java回的标准输出不完整，不知道为什么。达人请帮忙看下。

c++代码：

#include <iostream>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

using namespace std;

void err_sys(string msg)
{
	cout << msg << endl;
	exit(-1);
}
int main()
{
	int input[2];
	int output[2];
	int pid;
	FILE *log;

	if(pipe(input)<0)
		err_sys("pipe input error");

	if(pipe(output)<0)
		err_sys("pipe output error");

	if((pid = fork()) < 0)
		err_sys("fork error");

	if(pid==0)
	{
		cout << "child proc" << endl;
		//child
		close(input[1]);
		close(output[0]);
		close(STDIN_FILENO);
		close(STDOUT_FILENO);
		close(STDERR_FILENO);

		if(dup2(input[0], STDIN_FILENO) != STDIN_FILENO)
			err_sys("dup2 error to stdin");

		if(dup2(output[1], STDOUT_FILENO) != STDOUT_FILENO)
			err_sys("dup2 error to stdout");

		if(dup2(output[1], STDERR_FILENO) != STDERR_FILENO)
			err_sys("dup2 error to stderr");

		/***process the buf***/
		system("java -cp /home/tiger/test/java ptest");
	}
	else
	{
		cout << "parent proc. child proc id=" << pid << endl;
		//parent
		close(input[0]);
		close(output[1]);

		char buf[100];

			string temp="input from c father";
			write(input[1], temp.c_str(), temp.length());
			while(true){
				sleep(2);
				int n= read(output[0], buf, 100);
				//buf[n]='\0';
				printf("c read length=%d, content=%s\n", n, buf);
			}
	}
	exit(0);
}

java代码：

import java.io.PrintWriter;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;


public class ptest {

public static void main(String args[]) throws Exception{
	System.out.println("java start0");
	
	BufferedReader consoleInput = new BufferedReader(new InputStreamReader(System.in));
	PrintWriter writer = new PrintWriter("output.log");
	writer.println("Start");
	writer.flush();
	boolean readflag = false;
	while(true){
		System.out.println("java start4");
		writer.println("enter while");
		writer.flush();
		try {
			System.out.println("java start5");
			for(String read; (read = consoleInput.readLine())!= null && read.length()>0;)
			{

				String str = "read in java: " + read;
				writer.println(str);
				writer.flush();
				System.out.println(str);
				//System.out.flush();
				read = "";
				readflag = true;
				writer.println("readline end");
				writer.flush();
			}
			writer.println("for end");
			writer.flush();
			if (readflag)
			{
				System.out.println("read end");
				//System.out.flush();
				writer.println("while end");
				writer.flush();
				break;
			}
			System.out.println("read continue");
			//System.out.flush();
		} 
		catch (IOException e) {
			e.printStackTrace();
		}
	}
	System.out.println("java end");
	//System.out.flush();
	writer.println("java end");
	writer.flush();
}


}

运行c++结果是：
# ./a.out
child proc
parent proc. child proc id=6295
c read length=36, content=java start0
java start4
java start5
?

java start5之后出现乱码，请教下是什么问题。多谢了。

[duotiger]

不能沉不能沉不能沉

[duotiger]

为什么没回复啊……不能沉不能沉！