[Tutor] REG : Pexpect timeout issue

[Cameron Simpson]

On 02Sep2018 14:29, Steven D'Aprano <steve at pearwood.info> wrote:
>On Sun, Sep 02, 2018 at 10:01:02AM +1000, Cameron Simpson wrote:
>> On 02Sep2018 00:31, Steven D'Aprano <steve at pearwood.info> wrote:
>> >On Sat, Sep 01, 2018 at 11:41:42AM +0000, krishna chaitanya via Tutor
>> >wrote:
>> >>Below is my code, i am frequently hitting timeout issue to login to linux
>> >>or router.
>> >
>> >Timeout issues are a network problem. Perhaps your network is too busy,
>> >or the cable is faulty, or your router is being hammered by attackers
>> >and can't respond.
>>
>> No, timeout issues are "the target input didn't arrive in this timeframe".
>>
>> All his commands are _local_.
>
>Krishna wrote:
>
>"i am frequently hitting timeout issue to login to linux or router."
>
>Given that Krishna says he's trying to login to a router, what tells you
>that it is local?

His script, which goes:

  import pexpect
  from pexpect import *
  child = spawn('su xxxxx',timeout = 50)
  child.expect('Password:',timeout = 50)
  child.sendline('XXXXXXX') #child.sendline('ls -l')#
  chasis = child.before.decode('utf-8')
  child.expect('krishna at krishna-desktop:~/python_excercises$',timeout = 50)
  child.sendline('ls -l')
  chasis = child.before.decode('utf-8')
  print(chasis)
 
  Error :
      raise TIMEOUT(msg)pexpect.exceptions.TIMEOUT: Timeout 
      exceeded.<pexpect.pty_spawn.spawn object at 0x7f068506fa20>

All his commands are local, with no remote login. He's probably just slightly 
misusing the term "timeout issue to login to linux" when tallking about "su".

The expect stuff matches command outputs against an expression. Any command 
which issues a prompt and pauses indefinitely, and whose prompt isn't matched 
by the expression, will inherently stall the output and cause a timeout if the 
expect() call has a timeout setting.

It could easily be that the su is working and that his pattern for his shell 
prompt is incorrect ("python_excercises" looks misspelled to me). Same 
situation and same symptom.

Cheers,
Cameron Simpson <cs at cskk.id.au>