error executing some of bash commands in python subprocess.call while few of them works like charm

Question

I am having an issue running bash commands from a python script. some of them works while others don't

ls command works

from subprocess import call
call(["ls"])

but I want to close some ports, but below command, don't seem to work

from subprocess import call
call(['lsof -ti:9938,9955,9910,9988 | xargs kill'])

gives an error

   /System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7 /Users/amar/Documents/vKey_XenServer/vkey/architectures/Reactive/deamons/test.py
Traceback (most recent call last):
  File "/Users/amar/Documents/vKey_XenServer/vkey/architectures/Reactive/deamons/test.py", line 2, in <module>
    call(['lsof -ti:a9938,9955,9910,9988 | xargs kill'])
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 522, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 710, in __init__
    errread, errwrite)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1335, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

so I tried some of the commands, few were working and others were not

For instance, top command works

from subprocess import call
call(['top'])

but, cd .. does not

from subprocess import call
call(['cd ..'])

gives an error

Traceback (most recent call last):
  File "/Users/amar/Documents/vKey_XenServer/vkey/architectures/Reactive/deamons/test.py", line 2, in <module>
    call(['cd ..'])
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 522, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 710, in __init__
    errread, errwrite)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1335, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory

I may be asking a rudimentary question, but how do I differentiate which shell command will work in python.

Thanks in advance guys 😀

everything should work , what error are you getting?

Stack
– Stack

2018-01-10 05:12:46 +00:00
Commented Jan 10, 2018 at 5:12 — Stack
– Stack, Commented Jan 10, 2018 at 5:12

pankaj mishra · Accepted Answer · 2018-01-10 06:26:55Z

1

For the command using PIPE , you need to redirect the output of one command to the input of other subprocess Popen class.

Below example should work for you

from subprocess import Popen
import shlex
input="lsof -ti:9938,9955,9910,9988"
command=shlex.split(input) #will split the command in list format
p1 = Popen(command, stdout=PIPE)
p2 = Popen(["xargs", "kill"], stdin=p1.stdout, stdout=PIPE)
p1.stdout.close()  # Allow p1 to receive a SIGPIPE if p2 exits.
output = p2.communicate()[0]

For detailed information you can refer here https://docs.python.org/2/library/subprocess.html

answered Jan 10, 2018 at 6:26

pankaj mishra

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DYZ · Accepted Answer · 2018-01-10 05:19:52Z

1

" cd .." is not a command; the command is "cd", and ".." is its argument. Consider passing ["cd", ".."]. Same with lsof.

answered Jan 10, 2018 at 5:19

DYZ

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2 Comments

Amarjit Dhillon Over a year ago

it worked, thanks for this update but how do I make lsof -ti:9938,9955,9910,9988 | xargs kill work ?

DYZ Over a year ago

You can not do this with call because there is a pipe involved.

Amarjit Dhillon · Accepted Answer · 2018-01-10 19:36:07Z

-1

another simple way of killing multiple ports is

from subprocess import call
call('pkill 50000 , 50001 , 50002 , 50003', shell=True)
print 'ports are closed'

answered Jan 10, 2018 at 19:36

Amarjit Dhillon

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