Unable to write to stdin in subprocess

Question

i am unable to pass in commands to stdin in python 3.2.5. I have tried with the following 2 approaches Also: This question is a continuation of a previous question.

from subprocess import Popen, PIPE, STDOUT
import time

p = Popen([r'fileLoc/uploader.exe'],shell = True, stdout=PIPE, stdin=PIPE, stderr=STDOUT)
p.stdin.write('uploader -i file.txt -d outputFolder\n')
print (p.communicate()[0])
p.stdin.close()

i also get numbers such as 96, 0, 85 returned to me when i try the code in the IDLE interpreter, along with errors such as from the print (p.communicate()[0])

Traceback (most recent call last):
  File "<pyshell#132>", line 1, in <module>
    p.communicate()[0]
  File "C:\Python32\lib\subprocess.py", line 832, in communicate
    return self._communicate(input)
  File "C:\Python32\lib\subprocess.py", line 1060, in _communicate
    self.stdin.close()
IOError: [Errno 22] Invalid argument

i have also used:

from subprocess import Popen, PIPE, STDOUT
    import time

    p = Popen([r'fileLoc/uploader.exe'],shell = True, stdout=PIPE, stdin=PIPE, stderr=STDOUT)
    p.communicate(input= bytes(r'uploader -i file.txt -d outputFolder\n','UTF-8'))[0]
    print (p.communicate()[0])
    p.stdin.close()

but with no luck.

score 0 · Answer 1 · answered Jun 26 '13 at 20:27

0

don't use shell=True when passing the arguments as list.
stdin.write needs a bytes object as argument. You try to wire a str.
communicate() writes input to the stdin and returns a tuple with the otput of stdout and sterr, and it waits until the process has finished. You can only use it once, trying to call it a second time will result in an error.
are your sure the line you're writing should be passed to your process on stdin? Shouldn't it be the command you're trying to run?

answered Jun 26 '13 at 20:27

mata

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1. Shell = True Solved 2. stdin.write: i solved this previously but i forgot to write it here, so now i have bytes(r'command','UTF-8') – Rohit Jun 26 '13 at 20:38
3. the communicate() is what is giving me the biggest problems, i keep getting the IOError: [Errno 22] Invalid argument Error. I am only calling it once, and the format i am using is as follows: output = p.communicate(input = 'whatever the input is')[0] Even when i write: print (p.communicate()[0]) it still gives me IOError: [Errno 22] Invalid argument Error – Rohit Jun 26 '13 at 20:53
4. it is a command i am trying to run, so i tried p = Popen([r'fileLoc/uploader.exe', 'command'],stdout=PIPE, stdin=PIPE, stderr=STDOUT) and p = Popen([r'fileLoc/uploader.exe'], stdout=PIPE, stdin=PIPE, stderr=STDOUT) and when i do p.stdout.readlines() i get the same login information – Rohit Jun 26 '13 at 20:54
have you tried `Popen([r'fileLoc/uploader.exe', '-i', 'file.txt', '-o', 'outputFolder'], ...)`? seems more reasonable to me. – mata Jun 26 '13 at 21:00
Mata, i am able to get past the login detail and to the login info section. So what this is doing is waits 5 secs then prompts me for my username, and then prompts me for my password. I tried p.stdin.write('username@email.com\n') But i dont think this is working, also when i type these statments in the idle interpreter, it returns some number such as 9, 30 ... can you explain what these are? – Rohit Jun 26 '13 at 21:34
1

`write` returns the number of bytes written to the stream, so that's what you're seeing in the interactive interperter session. Programs reading username/passwords are usually designed to read from a terminal, so often they don't work well when you send them data on stdin – mata Jun 26 '13 at 21:39

score 0 · Answer 2 · edited May 23 '17 at 12:11

0

Pass command arguments as arguments, not as stdin
The command might read username/password from console directly without using subprocess' stdin. In this case you might need winpexpect or SendKeys modules. See my answer to a similar quesiton that has corresponding code examples

Here's an example how to start a subprocess with arguments, pass some input, and write merged subprocess' stdout/stderr to a file:

#!/usr/bin/env python3
import os
from subprocess import Popen, PIPE, STDOUT

command = r'fileLoc\uploader.exe -i file.txt -d outputFolder'# use str on Windows
input_bytes = os.linesep.join(["username@email.com", "password"]).encode("ascii")
with open('command_output.txt', 'wb') as outfile:
    with Popen(command, stdin=PIPE, stdout=outfile, stderr=STDOUT) as p:
        p.communicate(input_bytes)

edited May 23 '17 at 12:11

Community

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answered Jun 27 '13 at 01:25

jfs

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Sebastian, the program that i am trying to run, seems to freeze. – Rohit Jun 27 '13 at 13:27
@Rohit: It probably waits for input. To test it, do not redirect the stdout and see whether it stops (freezes) at a prompt (for username, password, etc). – jfs Jun 27 '13 at 14:13
ya i tried without the stdout = outfile, and it still seems to be frozen. i think there is an error with the starting the program itself – Rohit Jun 27 '13 at 14:46
I've meant that without the redirection, you should be able to see the subprocess output – to find out where it blocks – jfs Jun 27 '13 at 14:53
ya unfortunately, i am unable to see the output even without the redirection. i will some thing out, and see if they work, and then ill tell you – Rohit Jun 27 '13 at 15:10

Unable to write to stdin in subprocess

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