java：如何读取和写入&从流程到管道（stdin / stdout） [英] java: how to both read and write to & from process thru pipe (stdin/stdout)

问题描述

（我是java的新手）
我需要启动一个进程并接收2或3个句柄：对于STDIN，STDOUT，（和STDERR），所以我可以向进程写入输入并接收其输出，与Python中的命令行管道行为相同（例如grep）

(i'm new to java) I need to start a process and receive 2 or 3 handles: for STDIN, STDOUT, (and STDERR), so I can write input to the process and receive its output, the same way command line pipes behave (e.g. "grep")

这是通过以下代码实现的：

in Python this is acheived with the following code:

from subprocess import Popen, PIPE
p = Popen(cmd, shell=True, stdin=PIPE, stdout=PIPE)
(child_stdin, child_stdout) = (p.stdin, p.stdout)
child_stdin.write('Yoram Opposum\n')
child_stdin.flush()
child_stdout.readlines()

什么是Java等价物？

What's the Java equivalent??

我到目前为止尝试过

Process p = Runtime.getRuntime().exec(cmd);
BufferedReader inp = new BufferedReader( new InputStreamReader(p.getInputStream()) );
BufferedWriter out = new BufferedWriter( new OutputStreamWriter(p.getOutputStream()) );
out.write( "Some Text!\n\n" );
out.flush();
line = inp.readLine();
print("response1: " + line );   // that's ok
out.write( "Second Line...\n" );
out.flush();
line = inp.readLine();
print("response2: " + line );    // returns an empty string, if it returns,,,
inp.close();
out.close();

BTW第一次尝试仅适用于\ n\ n，但不适用于单身\ n（为什么？）

BTW the first try works only with \n\n, but doesn't work with single \n (why?)

以下代码有效，但所有输入都是事先给出的，而不是我正在寻找的行为：

the following code works, but all input is given in advance, not the behavior i'm looking for:

out.write( "Aaaaa\nBbbbbb\nCcccc\n" );
out.flush();
line = inp.readLine();
print("response1: " + line );
line = inp.readLine();
print("response2: " + line );
line = inp.readLine();
print("response3: " + line );
line = inp.readLine();
print("response4: " + line );

输出：

response1: AAAAA
response2: 
response3: bbbbbb
response4: 

正在运行的过程如下：

s = sys.stdin.readline()
print s.upper()
s = sys.stdin.readline()
print s.lower()

推荐答案

好吧，这也是我的python代码错误，但与@ Jon的答案相反，有一个EXTRA换行符（确切地说是0xA0，这不是Windows'标准）。

ok, it was also my python's code fault, but opposite to @Jon's answer, there was an EXTRA newline (0xA0 to be exact, which isn't Windows' standard).

一旦我从Java中获取额外的0xA0，python就会添加一个正常\ n到Java在回来的路上，事情顺利进行。

once i'm strip()ing the extra 0xA0 from the line i get from Java, python adds a single "normal" \n to Java on the way back, and things run smoothly.

问题和答案的完整性，这是一个可用的Java代码：

for the completeness of the question and answer, here's a working Java code:

import java.io.*;
import java.util.*;

public class Main {

    public static BufferedReader inp;
    public static BufferedWriter out;

    public static void print(String s) {
    System.out.println(s);
    }

    public static String pipe(String msg) {
    String ret;

    try {
        out.write( msg + "\n" );
        out.flush();
        ret = inp.readLine();
        return ret;
    }
    catch (Exception err) {

    }
    return "";
    }



    public static void main(String[] args) {

    String s;
    String cmd = "c:\\programs\\python\\python.exe d:\\a.py";

    try {

        print(cmd);
        print(System.getProperty("user.dir"));
        Process p = Runtime.getRuntime().exec(cmd);

        inp = new BufferedReader( new InputStreamReader(p.getInputStream()) );
        out = new BufferedWriter( new OutputStreamWriter(p.getOutputStream()) );

        print( pipe("AAAaaa") );
        print( pipe("RoteM") );

        pipe("quit")
        inp.close();
        out.close();
    }

    catch (Exception err) {
        err.printStackTrace();
    }
    }
}

这是python代码

import sys
s = sys.stdin.readline().strip()
while s not in ['break', 'quit']:
    sys.stdout.write(s.upper() + '\n')
    sys.stdout.flush()
    s = sys.stdin.readline().strip()

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