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Opening interactive python shell after running python script in background

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0

python3 -i test.py opens an interactive python shell after running test.py. However, if I try to run it in the background with python3 -i test.py &
the job stops automatically with a ^C and shows

[4]+  Stopped                 python3 -i test.py

, and I can't access python's interactive shell (with the variables from test.py still in the environment) afterwards. fging the process (i.e. fg %4) leads to an interactive shell where my input can't be seen but is still run after pressing <Enter>. How do I run the interactive shell "normally" after running test.py in the background?

(For reference, test.py contains

from time import sleep

a = 'hello world'

for i in range(10):

    sleep(1)

    print(a)

and my shell looks like this:

$ python3 -i test.py &

[4] 6708

$ hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

fg %4

python3 -i test.py

>>> 'hello world'

>>>

and I typed a after being prompted by the first >>>, but it isn't shown.
)

-- Edit @muru --

Sending it to the bg after running it normally in the fg gives:

$

$

$ python3 -i test.py

hello world

hello world

hello world

hello world

^Z

[4]+  Stopped                 python3 -i test.py

$ bg %4

[4]+ python3 -i test.py &

$ hello world

hello world

hello world

hello world

hello world

hello world

echo 'hello world'

hello world



[4]+  Stopped                 python3 -i test.py

$

$

where shell was expecting input and I typed echo 'hello world' after the 10 "Hello World"'s.

shell python background-process jobs interactive

share|improve this question

edited 13 hours ago

Anonymous

asked 2 days ago

AnonymousAnonymous

833 bronze badges

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Anonymous is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Why would an interactive process be run in the background?
  
  – muru
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I want to run a python file that takes quite some time, and do other things with the same terminal in the meantime, but still examine the script’s environment (interactively) when it’s done running.
  
  – Anonymous
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Try sending it to the background after starting it normally (Ctrl-Z then bg).
  
  – muru
  2 days ago
  

  
  
  
  

add a comment | 

1

0

python3 -i test.py opens an interactive python shell after running test.py. However, if I try to run it in the background with python3 -i test.py &
the job stops automatically with a ^C and shows

[4]+  Stopped                 python3 -i test.py

, and I can't access python's interactive shell (with the variables from test.py still in the environment) afterwards. fging the process (i.e. fg %4) leads to an interactive shell where my input can't be seen but is still run after pressing <Enter>. How do I run the interactive shell "normally" after running test.py in the background?

(For reference, test.py contains

from time import sleep

a = 'hello world'

for i in range(10):

    sleep(1)

    print(a)

and my shell looks like this:

$ python3 -i test.py &

[4] 6708

$ hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

fg %4

python3 -i test.py

>>> 'hello world'

>>>

and I typed a after being prompted by the first >>>, but it isn't shown.
)

-- Edit @muru --

Sending it to the bg after running it normally in the fg gives:

$

$

$ python3 -i test.py

hello world

hello world

hello world

hello world

^Z

[4]+  Stopped                 python3 -i test.py

$ bg %4

[4]+ python3 -i test.py &

$ hello world

hello world

hello world

hello world

hello world

hello world

echo 'hello world'

hello world



[4]+  Stopped                 python3 -i test.py

$

$

where shell was expecting input and I typed echo 'hello world' after the 10 "Hello World"'s.

shell python background-process jobs interactive

share|improve this question

edited 13 hours ago

Anonymous

asked 2 days ago

AnonymousAnonymous

833 bronze badges

New contributor

Anonymous is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Why would an interactive process be run in the background?
  
  – muru
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I want to run a python file that takes quite some time, and do other things with the same terminal in the meantime, but still examine the script’s environment (interactively) when it’s done running.
  
  – Anonymous
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Try sending it to the background after starting it normally (Ctrl-Z then bg).
  
  – muru
  2 days ago
  

  
  
  
  

add a comment | 

python3 -i test.py opens an interactive python shell after running test.py. However, if I try to run it in the background with python3 -i test.py &
the job stops automatically with a ^C and shows

[4]+  Stopped                 python3 -i test.py

, and I can't access python's interactive shell (with the variables from test.py still in the environment) afterwards. fging the process (i.e. fg %4) leads to an interactive shell where my input can't be seen but is still run after pressing <Enter>. How do I run the interactive shell "normally" after running test.py in the background?

(For reference, test.py contains

from time import sleep

a = 'hello world'

for i in range(10):

    sleep(1)

    print(a)

and my shell looks like this:

$ python3 -i test.py &

[4] 6708

$ hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

fg %4

python3 -i test.py

>>> 'hello world'

>>>

and I typed a after being prompted by the first >>>, but it isn't shown.
)

-- Edit @muru --

Sending it to the bg after running it normally in the fg gives:

$

$

$ python3 -i test.py

hello world

hello world

hello world

hello world

^Z

[4]+  Stopped                 python3 -i test.py

$ bg %4

[4]+ python3 -i test.py &

$ hello world

hello world

hello world

hello world

hello world

hello world

echo 'hello world'

hello world



[4]+  Stopped                 python3 -i test.py

$

$

where shell was expecting input and I typed echo 'hello world' after the 10 "Hello World"'s.

shell python background-process jobs interactive

share|improve this question

edited 13 hours ago

Anonymous

asked 2 days ago

AnonymousAnonymous

833 bronze badges

New contributor

Anonymous is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

[4]+  Stopped                 python3 -i test.py

from time import sleep

a = 'hello world'

for i in range(10):

    sleep(1)

    print(a)

$ python3 -i test.py &

[4] 6708

$ hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

hello world

fg %4

python3 -i test.py

>>> 'hello world'

>>>

$

$

$ python3 -i test.py

hello world

hello world

hello world

hello world

^Z

[4]+  Stopped                 python3 -i test.py

$ bg %4

[4]+ python3 -i test.py &

$ hello world

hello world

hello world

hello world

hello world

hello world

echo 'hello world'

hello world



[4]+  Stopped                 python3 -i test.py

$

$

share|improve this question

edited 13 hours ago

Anonymous

asked 2 days ago

AnonymousAnonymous

833 bronze badges

New contributor

Anonymous is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 13 hours ago

Anonymous

asked 2 days ago

AnonymousAnonymous

833 bronze badges

New contributor

Anonymous is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 days ago

AnonymousAnonymous

833 bronze badges

New contributor

Anonymous is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 days ago

AnonymousAnonymous

833 bronze badges

1 Answer
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That happens because the Python interpreter in background "competes" the prompt with the command-line shell as soon as it finishes executing the test.py program.

Naturally Python loses that "battle" because it is not the one allowed to go interactive at that moment. However it gets stopped a bit too late, enough to leave its own prompt in a state that will not resume cleanly on an fg command.

One way to settle this is by adding the following lines at the end of your Python program:

import os, signal  # access os-level functions and UNIX-signals

os.kill(os.getpid(), signal.SIGSTOP)  # send myself the UNIX SIGSTOP signal

(Of course the import can also be placed on top of your program as per typical practice.)

That os.kill() line will put the Python interpreter in stopped state, just like it gets when it tries to go interactive at the wrong moment. Only, this time it does it itself, before even attempting to prompt, so that it is not left in an inconsistent state.

You know when that os.kill() is reached because the command-line shell notifies you that Python got Stopped. An fg at that moment will resume Python making it proceed from the os.kill() line, thus starting its own interactive session.

Don't use bg to resume it after it got Stopped by that os.kill(), because doing so will only make the kernel stop Python again for attempting to go interactive while in background.

share|improve this answer

edited 13 hours ago

answered yesterday

LL3LL3

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0

That happens because the Python interpreter in background "competes" the prompt with the command-line shell as soon as it finishes executing the test.py program.

Naturally Python loses that "battle" because it is not the one allowed to go interactive at that moment. However it gets stopped a bit too late, enough to leave its own prompt in a state that will not resume cleanly on an fg command.

One way to settle this is by adding the following lines at the end of your Python program:

import os, signal  # access os-level functions and UNIX-signals

os.kill(os.getpid(), signal.SIGSTOP)  # send myself the UNIX SIGSTOP signal

(Of course the import can also be placed on top of your program as per typical practice.)

That os.kill() line will put the Python interpreter in stopped state, just like it gets when it tries to go interactive at the wrong moment. Only, this time it does it itself, before even attempting to prompt, so that it is not left in an inconsistent state.

You know when that os.kill() is reached because the command-line shell notifies you that Python got Stopped. An fg at that moment will resume Python making it proceed from the os.kill() line, thus starting its own interactive session.

Don't use bg to resume it after it got Stopped by that os.kill(), because doing so will only make the kernel stop Python again for attempting to go interactive while in background.

share|improve this answer

edited 13 hours ago

answered yesterday

LL3LL3

2,16211 silver badge1414 bronze badges

add a comment | 

0

That happens because the Python interpreter in background "competes" the prompt with the command-line shell as soon as it finishes executing the test.py program.

Naturally Python loses that "battle" because it is not the one allowed to go interactive at that moment. However it gets stopped a bit too late, enough to leave its own prompt in a state that will not resume cleanly on an fg command.

One way to settle this is by adding the following lines at the end of your Python program:

import os, signal  # access os-level functions and UNIX-signals

os.kill(os.getpid(), signal.SIGSTOP)  # send myself the UNIX SIGSTOP signal

(Of course the import can also be placed on top of your program as per typical practice.)

That os.kill() line will put the Python interpreter in stopped state, just like it gets when it tries to go interactive at the wrong moment. Only, this time it does it itself, before even attempting to prompt, so that it is not left in an inconsistent state.

You know when that os.kill() is reached because the command-line shell notifies you that Python got Stopped. An fg at that moment will resume Python making it proceed from the os.kill() line, thus starting its own interactive session.

Don't use bg to resume it after it got Stopped by that os.kill(), because doing so will only make the kernel stop Python again for attempting to go interactive while in background.

share|improve this answer

edited 13 hours ago

answered yesterday

LL3LL3

2,16211 silver badge1414 bronze badges

add a comment | 

That happens because the Python interpreter in background "competes" the prompt with the command-line shell as soon as it finishes executing the test.py program.

Naturally Python loses that "battle" because it is not the one allowed to go interactive at that moment. However it gets stopped a bit too late, enough to leave its own prompt in a state that will not resume cleanly on an fg command.

One way to settle this is by adding the following lines at the end of your Python program:

import os, signal  # access os-level functions and UNIX-signals

os.kill(os.getpid(), signal.SIGSTOP)  # send myself the UNIX SIGSTOP signal

(Of course the import can also be placed on top of your program as per typical practice.)

That os.kill() line will put the Python interpreter in stopped state, just like it gets when it tries to go interactive at the wrong moment. Only, this time it does it itself, before even attempting to prompt, so that it is not left in an inconsistent state.

You know when that os.kill() is reached because the command-line shell notifies you that Python got Stopped. An fg at that moment will resume Python making it proceed from the os.kill() line, thus starting its own interactive session.

Don't use bg to resume it after it got Stopped by that os.kill(), because doing so will only make the kernel stop Python again for attempting to go interactive while in background.

share|improve this answer

edited 13 hours ago

answered yesterday

LL3LL3

2,16211 silver badge1414 bronze badges

import os, signal  # access os-level functions and UNIX-signals

os.kill(os.getpid(), signal.SIGSTOP)  # send myself the UNIX SIGSTOP signal

share|improve this answer

edited 13 hours ago

answered yesterday

LL3LL3

2,16211 silver badge1414 bronze badges

answered yesterday

LL3LL3

2,16211 silver badge1414 bronze badges

answered yesterday

LL3LL3

2,16211 silver badge1414 bronze badges