Python how to read output from pexpect child?

Question

child = pexpect.spawn ('/bin/bash')
child.sendline('ls')
print(child.readline())
print child.before, child.after

All I get with this code in my output is

ls

ls 

But when my code is

child = pexpect.spawn('ls')
print(child.readline())
print child.before, child.after

Then it works, but only for the first 2 prints. Am I using the wrong send command? I tried send, write, sendline, and couldn't find anymore.

Answer 1

In pexpect the before and after attributes are populated after an expect method. The most common thing used in this situation is waiting for the prompt (so you'll know that the previous command finished execution). So, in your case, the code might look something like this:

child = pexpect.spawn ('/bin/bash')
child.expect("Your bash prompt here")
child.sendline('ls')
#If you are using pxssh you can use this
#child.prompt()
child.expect("Your bash prompt here")
print(child.before)

Answer 2

Try the following:

import pexpect
child = pexpect.spawn('ls')
print child.read() # not readline

The read() will give you the entire output of the ls.

Answer 3

#!/usr/bin/env python

import pexpect
child = pexpect.spawn("ssh root@172.16.0.120c -p 2222")
child.logfile = open("/tmp/mylog", "w")
child.expect(".*assword:")
child.send("XXXXXXX\r")
child.expect(".*\$ ")
child.sendline("ls\r")
child.expect(".*\$ ")

go to open your logfile:- go to terminal

$gedit /tmp/mylog

As Per https://pexpect.readthedocs.io/en/stable/api/pexpect.html#spawn-class

# In Python 3, we'll use the ``encoding`` argument to decode data
# from the subprocess and handle it as unicode:
 child = pexpect.spawn('some_command', encoding='utf-8')
 child.logfile = sys.stdout

Answer 4

I think all you need is:

p = pexpect.spawn('ls')
p.expect(pexpect.EOF)
print(p.before)

or

p = pexpect.spawn('/bin/ls')
p.expect(pexpect.EOF)
print(p.before)

or

p = pexpect.spawn('/bin/bash -c "ls"')
p.expect(pexpect.EOF)
print(p.before)

or even

print(pexpect.run('ls'))

Answer 5

import sys
import pexpect
child = pexpect.spawn('ls')
child.logfile = sys.stdout
child.expect(pexpect.EOF)

See the manual entry on the subject.

Answer 6

copy from class spawn(SpawnBase) docstring, maybe example-2 is what you want.

Example log input and output to a file::

child = pexpect.spawn('some_command')
fout = open('mylog.txt','wb')
child.logfile = fout

Example log to stdout::

# In Python 2:
child = pexpect.spawn('some_command')
child.logfile = sys.stdout

# In Python 3, we'll use the ``encoding`` argument to decode data
# from the subprocess and handle it as unicode:
child = pexpect.spawn('some_command', encoding='utf-8')
child.logfile = sys.stdout

Answer 7

You can use a simple package tiotrap , which contains TextIOTrap helper class for managing TextIO Streams.

Installation:

python3 -m pip install tiotrap

For example:

tio_trap = tiotrap.TextIOTrap(store=True)
p = pexpect.spawn('ls -la')
p.logfile = tio_trap
p.expect(pexpect.EOF)
print(f"ls output:\n{str(tio_trap)}\n~")

Answer 8

for me the logfile approach wasn't working as it contained a bunch of escape characters I couldn't get rid off.

I ended up echoing the cmd-output, eg if your OS is ubuntu:

child.sendline(yourcommand > logfile.txt)