Python 从需要 stdin 的子进程实时打印 stdout
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printing stdout in realtime from a subprocess that requires stdin
提问by hatmatrix
This is a follow up to this question, but if I want to pass an argument to stdinto subprocess, how can I get the output in real time? This is what I currently have; I also tried replacing Popenwith callfrom the subprocessmodule and this just leads to the script hanging.
这是对这个问题的跟进，但如果我想将参数传递stdin给subprocess，我怎样才能实时获得输出？这就是我目前拥有的；我也尝试从模块中替换Popen，这只会导致脚本挂起。callsubprocess
from subprocess import Popen, PIPE, STDOUT
cmd = 'rsync --rsh=ssh -rv --files-from=- thisdir/ servername:folder/'
p = Popen(cmd.split(), stdout=PIPE, stdin=PIPE, stderr=STDOUT)
subfolders = '\n'.join(['subfolder1','subfolder2'])
output = p.communicate(input=subfolders)[0]
print output
In the former question where I did not have to pass stdinI was suggested to use p.stdout.readline, there there is no room there to pipe anything to stdin.
在我不必通过的前一个问题中，我stdin被建议使用p.stdout.readline，那里没有空间可以将任何东西通过管道输送到stdin.
Addendum: This works for the transfer, but I see the output only at the end and I would like to see the details of the transfer while it's happening.
附录：这适用于转移，但我只在最后看到输出，我想在转移发生时查看转移的详细信息。
采纳答案by Alp
In order to grab stdout from the subprocess in real time you need to decide exactly what behavior you want; specifically, you need to decide whether you want to deal with the output line-by-line or character-by-character, and whether you want to block while waiting for output or be able to do something else while waiting.
为了实时从子进程中获取标准输出，您需要准确决定您想要什么行为；具体来说，您需要决定是要逐行处理输出还是逐字符处理输出，以及是在等待输出时阻塞还是在等待时能够做其他事情。
It looks like it will probably suffice for your case to read the output in line-buffered fashion, blocking until each complete line comes in, which means the convenience functions provided by subprocessare good enough:
看起来您的情况以行缓冲方式读取输出可能就足够了，阻塞直到每个完整的行进来，这意味着提供的便利功能subprocess已经足够好了：
p = subprocess.Popen(some_cmd, stdout=subprocess.PIPE)
# Grab stdout line by line as it becomes available. This will loop until
# p terminates.
while p.poll() is None:
l = p.stdout.readline() # This blocks until it receives a newline.
print l
# When the subprocess terminates there might be unconsumed output
# that still needs to be processed.
print p.stdout.read()
If you need to write to the stdin of the process, just use another pipe:
如果您需要写入进程的标准输入，只需使用另一个管道：
p = subprocess.Popen(some_cmd, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
# Send input to p.
p.stdin.write("some input\n")
p.stdin.flush()
# Now start grabbing output.
while p.poll() is None:
l = p.stdout.readline()
print l
print p.stdout.read()
Pacethe other answer, there's no need to indirect through a file in order to pass input to the subprocess.
吴佩慈对方的回答，没有必要通过间接以文件通过输入到子进程。
回答by Joran Beasley
something like this I think
我认为这样的事情
from subprocess import Popen, PIPE, STDOUT
p = Popen('c:/python26/python printingTest.py', stdout = PIPE,
stderr = PIPE)
for line in iter(p.stdout.readline, ''):
print line
p.stdout.close()
using an iterator will return live results basically ..
使用迭代器基本上会返回实时结果..
in order to send input to stdin you would need something like
为了将输入发送到标准输入，您需要类似的东西
other_input = "some extra input stuff"
with open("to_input.txt","w") as f:
f.write(other_input)
p = Popen('c:/python26/python printingTest.py < some_input_redirection_thing',
stdin = open("to_input.txt"),
stdout = PIPE,
stderr = PIPE)
this would be similar to the linux shell command of
这将类似于 linux shell 命令
%prompt%> some_file.o < cat to_input.txt
see alps answer for better passing to stdin
请参阅 alps 答案以更好地传递到标准输入
回答by jfs
If you pass all your input before starting reading the output and if by "real-time" you mean whenever the subprocess flushes its stdout buffer:
如果在开始读取输出之前传递所有输入，并且“实时”表示子进程刷新其标准输出缓冲区时：
from subprocess import Popen, PIPE, STDOUT
cmd = 'rsync --rsh=ssh -rv --files-from=- thisdir/ servername:folder/'
p = Popen(cmd.split(), stdout=PIPE, stdin=PIPE, stderr=STDOUT, bufsize=1)
subfolders = '\n'.join(['subfolder1','subfolder2'])
p.stdin.write(subfolders)
p.stdin.close() # eof
for line in iter(p.stdout.readline, ''):
print line, # do something with the output here
p.stdout.close()
rc = p.wait()
