从程序获取带有用户输入的程序输出

Question

我正在尝试从子流程的输出中捕获字符串，并且当子流程要求用户输入时，请将用户输入包括在字符串中，但是我无法使stdout正常工作。

我使用while循环从stdout获得了字符串输出，但是在读取字符串之后我不知道如何终止它。

我尝试使用subprocess.check_output ，但随后看不到用户输入的提示。

import subprocess
import sys
child = subprocess.Popen(["java","findTheAverage"], stdout = subprocess.PIPE, stdin = subprocess.PIPE )
string = u""

while True:
    line = str(child.stdout.read(1))
    if line != '':
        string += line[2]
        print(string)
    else:
        break

print(string)
for line in sys.stdin:
    print(line)
    child.stdin.write(bytes(line, 'utf-8'))

---

编辑：

有了Alfe post的帮助和代码，我现在有了从子流程程序输出中创建的字符串，并且用户对该程序进行了输入，但是混乱了。

该字符串似乎首先获取输出的第一个字母，然后是用户输入，然后是输出的其余部分。

字符串混淆的示例：

U2
3ser! please enter a double:U
4ser! please enter another double: U
5ser! please enter one final double: Your numbers were:
a = 2.0
b = 3.0
c = 4.0
average = 3.0

的意思是：

User! please enter a double:2
User! please enter another double: 3
User! please enter one final double: 4
Your numbers were:
a = 2.0
b = 3.0
c = 4.0
average = 3.0

使用代码：

import subprocess
import sys
import signal
import select


def signal_handler(signum, frame):
    raise Exception("Timed out!")


child = subprocess.Popen(["java","findTheAverage"], universal_newlines = True, stdout = subprocess.PIPE, stdin = subprocess.PIPE )
string = u""
stringbuf = ""

while True:
  print(child.poll())
  if child.poll() != None and not stringbuf:
    break
  signal.signal(signal.SIGALRM, signal_handler)
  signal.alarm(1)
  try:
    r, w, e = select.select([ child.stdout, sys.stdin ], [], [])
    if child.stdout in r:
        stringbuf = child.stdout.read(1)
        string += stringbuf
        print(stringbuf)
  except:
    print(string)
    print(stringbuf)
  if sys.stdin in r:
    typed = sys.stdin.read(1)
    child.stdin.write(typed)
    string += typed

---

最终编辑：

好吧，我试用了它，并使其与以下代码一起使用：

import subprocess
import sys
import select
import fcntl
import os

# the string that we will return filled with tasty program output and user input #
string = ""

# the subprocess running the program #
child = subprocess.Popen(["java","findTheAverage"],bufsize = 0, universal_newlines = True, stdout = subprocess.PIPE, stdin = subprocess.PIPE )

# stuff to stop IO blocks in child.stdout and sys.stdin ## (I stole if from  http://stackoverflow.com/a/8980466/2674170)
fcntl.fcntl(child.stdout.fileno(), fcntl.F_SETFL, os.O_NONBLOCK)
fcntl.fcntl(sys.stdin.fileno(), fcntl.F_SETFL, os.O_NONBLOCK)

# this here in the unlikely event that the program has #
# finished by the time the main loop is first running  #
# because if that happened the loop would end without  #
# having added the programs output to the string!      #
progout = ""
typedbuf = "#"

### here we have the main loop, this friendly fellah is 
### going to read from the program and user, and tell
### each other what needs to be known
while True:

## stop when the program finishes and there is no more output
  if child.poll() != None and not progout:
    break

# read from 
  typed = ""

  while typedbuf:
    try:
      typedbuf = sys.stdin.read(1)
    except:
      break
    typed += typedbuf
    stringbuf  = "#"
  string += typed
  child.stdin.write(typed)

  progout = ""
  progoutbuf = "#"
  while progoutbuf:
    try:
      progoutbuf = child.stdout.read(1)
    except:
      typedbuf = "#"
      break 
    progout += progoutbuf
  if progout:
    print(progout)
  string += progout

# the final output string #
print( string)

Answer 1

您需要select同时读取多个源（在您的情况下为stdin和子进程的输出）。

import select

string = ''
while True:
  r, w, e = select.select([ child.stdout, sys.stdin ], [], [])
  if child.stdout in r:
    string += child.stdout.read()
  if sys.stdin in r:
    typed = sys.stdin.read()
    child.stdin.write(typed)
    string += typed

您仍然需要找到合适的中断条件才能退出该循环。 但是您可能已经知道了。

在这一点上，我想发出警告：写入管道的进程通常会缓冲到最新的时刻； 您可能不会想到这一点，因为从命令行（在终端中）测试同一程序时，通常仅缓冲行。 这是出于性能方面的考虑。 写入终端时，通常用户希望尽快看到输出。 在写入管道时，通常会为读取过程提供较大的块，以便在它们到达之前休眠更长时间。