Develop Reference

How to save the last output in variable when hit KeyboardInterrupt subprocess

I am completely new to the subprocess module. And I was trying to automate the deauthentication attack commands. When I run airodump-ng wlan0mon as you know it looks for the APs nearby and the connected clients to it.
Now when I try to run this command using lets suppose p = subprocess.run(["airmon-ng","wlan0mon"], capture_output=True) in Python as you know this command runs until the user hits Ctrl+C, so it should save the last output when user hits Ctrl+C in the variable but instead I get error which is this:
Traceback (most recent call last):
File "Deauth.py", line 9, in <module>
p3 = subprocess.run(["airodump-ng","wlan0"], capture_output=True)
File "/usr/lib/python3.8/subprocess.py", line 491, in run
stdout, stderr = process.communicate(input, timeout=timeout)
File "/usr/lib/python3.8/subprocess.py", line 1024, in communicate
stdout, stderr = self._communicate(input, endtime, timeout)
File "/usr/lib/python3.8/subprocess.py", line 1866, in _communicate
ready = selector.select(timeout)
File "/usr/lib/python3.8/selectors.py", line 415, in select
fd_event_list = self._selector.poll(timeout)
KeyboardInterrupt
What can I try to resolve this?

Just use Python's error handling. Catch any KeyboardInnterrupts (within your subprocess function) using try and except statements like so:
def stuff(things):
try:
# do stuff
except KeyboardInterrupt:
return last_value

How does Jenkins deal with python scripts with Popen

We use Jenkins to run our cronjobs. We run Centos 6.8 on our server. Jenkins is version 1.651.
I'm running into a funny problem. When I run my script from the terminal, it works fine. I don't get any errors.
When I run the same script in Jenkins, it fails and says there's no such file or directory.
The error message from the Jenkins output I get is this:
Traceback (most recent call last):
File "runMTTRScript.py", line 256, in <module>
main()
File "runMTTRScript.py", line 252, in main
startTest(start, end, impalaHost)
File "runMTTRScript.py", line 72, in startTest
getResults(start, end)
File "runMTTRScript.py", line 111, in getResults
proc1 = subprocess.Popen(cmd, stdout=processlistOut)
File "/glide/lib64/python2.7/subprocess.py", line 710, in __init__
errread, errwrite)
File "/glide/lib64/python2.7/subprocess.py", line 1335, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory
Here's the code that the error above is complaining about:
with open(JAVAOUT + "_processList" + outfileDate, 'w') as processlistOut, \
open(JAVAOUT + "_innodb" + outfileDate, 'w') as innodbOut:
cmd = ["java", "-cp", "MTTR4hrs-1.0.5-SNAPSHOT-allinone.jar", "com.servicenow.bigdata.MTTR4hrs", "-c", "config.properties", "-m", DBIFILE, "-d", start, end, "-f", "processlist", "-ds", "dbi"]
proc1 = subprocess.Popen(cmd, stdout=processlistOut)
cmd = ["java", "-cp", "MTTR4hrs-1.0.5-SNAPSHOT-allinone.jar", "com.servicenow.bigdata.MTTR4hrs", "-c", "config.properties", "-m", DBIFILE, "-d", start, end, "-f", "engineinnodbstatus", "-ds", "dbi"]
proc2 = subprocess.Popen(cmd, stdout=innodbOut)
Why would it complain that a file is not there from Jenkins but be fine when I run it from cmd line? Could this also be some race condition in python that I'm not aware of too? The "with...open" doesn't open a file fast enough for the Popen to make use of? I'm also open to the fact that it might be some OS problem too (too many open files, something stupid, etc.).

data stream python subprocess.check_output exe from another location

I would like to run an exe from this directory:/home/pi/pi_sensors-master/bin/Release/
This exe is then run by tying mono i2c.exe and it runs fine.
I would like to get this output in python which is in a completely different directory.
I know that I should use subprocess.check_output to take the output as a string.
I tried to implement this in python:
import subprocess
import os
cmd = "/home/pi/pi_sensors-master/bin/Release/"
os.chdir(cmd)
process=subprocess.check_output(['mono i2c.exe'])
print process
However, I received this error:
The output would usually be a data stream with a new number each time, is it possible to capture this output and store it as a constantly changing variable?
Any help would be greatly appreciated.

Your command syntax is incorrect, which is actually generating the exception. You want to call mono i2c.exe, so your command list should look like:
subprocess.check_output(['mono', 'i2c.exe']) # Notice the comma separation.
Try the following:
import subprocess
import os
executable = "/home/pi/pi_sensors-master/bin/Release/i2c.exe"
print subprocess.check_output(['mono', executable])
The sudo is not a problem as long as you give the full path to the file and you are sure that running the mono command as sudo works.
I can generate the same error by doing a ls -l:
>>> subprocess.check_output(['ls -l'])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/subprocess.py", line 537, in check_output
process = Popen(stdout=PIPE, *popenargs, **kwargs)
File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
errread, errwrite)
File "/usr/lib/python2.7/subprocess.py", line 1249, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory
However when you separate the command from the options:
>>> subprocess.check_output(['ls', '-l'])
# outputs my entire folder contents which are quite large.
I strongly advice you to use the subprocess.Popen -object to deal with external processes. Use Popen.communicate() to get the data from both stdout and stderr. This way you should not run into blocking problems.
import os
import subprocess
executable = "/home/pi/pi_sensors-master/bin/Release/i2c.exe"
proc = subprocess.Popen(['mono', executable])
try:
outs, errs = proc.communicate(timeout=15) # Times out after 15 seconds.
except TimeoutExpired:
proc.kill()
outs, errs = proc.communicate()
Or you can call the communicate in a loop if you want a 'data-stream' of sort, an answer from this question:
from subprocess import Popen, PIPE
executable = "/home/pi/pi_sensors-master/bin/Release/i2c.exe"
p = Popen(["mono", executable], stdout=PIPE, bufsize=1)
for line in iter(p.stdout.readline, b''):
print line,
p.communicate() # close p.stdout, wait for the subprocess to exit

subprocess.call() for shell program which write a file

I need to execute a shell script using python. Output of shell program is a text file. No inputs to the script. Help me to resolve this.
def invokescript( shfile ):
s=subprocess.Popen(["./Script1.sh"],stderr=subprocess.PIPE,stdin=subprocess.PIPE);
return;
invokescript("Script1.sh");
On using above code., I receive the following error.
Traceback (most recent call last):
File "./test4.py", line 12, in <module>
invokescript("Script1.sh");
File "./test4.py", line 8, in invokescript
s=subprocess.Popen(["./Script1.sh"],stderr=subprocess.PIPE,stdin=subprocess.PIPE);
File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
errread, errwrite)
File "/usr/lib/python2.7/subprocess.py", line 1249, in _execute_child
raise child_exception
OSError: [Errno 8] Exec format error
Thanks in advance...

Try this:
import shlex
def invokescript(shfile):
return subprocess.Popen(
shlex.split(shfile),
stderr=subprocess.PIPE,
stdin=subprocess.PIPE
)
invokescript("Script1.sh");
And add #!/usr/bin/env bash to your bash file of course.

I used os.system() to call shell script. This do what i expected. Make sure that you have imported os module in your python code.
invokescript( "Script1.sh" ) // Calling Function
function invokescript( shfile ): // Function Defenition
os.system("/root/Saranya/Script1.sh")
return;
following is also executable:
invokescript( "Script1.sh" ) // Calling Function
function invokescript( shfile ): // Function Defenition
os.system(shfile)
return;
Thanks for your immediate response guys.

Python read windows Command Line output

I am trying to execute a command in python and read its output on command line in windows.
I have written the following code so far:
def build():
command = "cobuild archive"
print "Executing build"
pipe = Popen(command,stdout=PIPE,stderr=PIPE)
while True:
line = pipe.stdout.readline()
if line:
print line
I want to execute the command cobuild archive in command line and read it's output. However, the above code is giving me this error.
File "E:\scripts\utils\build.py", line 33, in build
pipe = Popen(command,stdout=PIPE,stderr=PIPE)
File "C:\Python27\lib\subprocess.py", line 679, in __init__
errread, errwrite)
File "C:\Python27\lib\subprocess.py", line 893, in _execute_child
startupinfo)
WindowsError: [Error 2] The system cannot find the file specified

The following code worked. I needed to pass shell=True for the arguments
def build():
command = "cobuild archive"
pipe = Popen(command,shell=True,stdout=PIPE,stderr=PIPE)
while True:
line = pipe.stdout.readline()
if line:
print line
if not line:
break

WindowsError: [Error 2] The system cannot find the file specified
This error says that the subprocess module is unable to locate your executable(.exe)
here "cobuild archive"
Suppose, if your executable in this path: "C:\Users\..\Desktop",
then, do,
import os
os.chdir(r"C:\Users\..\Desktop")
and then use your subprocess

Do you mind to post your code with the correct indentations please? They have a large effect in python - another way of doing this is:
import commands
# the command to execute
cmd = "cobuild archive"
# execute and get stdout
output = commands.getstatusoutput( cmd )
# do something with output
# ...
Update:
The commands module has been removed in Python 3, so this is a solution for python 2 only.
https://docs.python.org/2/library/commands.html