Develop Reference

Run shell script in python with specific parameters

I wish to run a script, lets call it api.sh. The script takes various arguments,
-t token
-r rules.json
-s data.json
and it is going to create a new json file, e.g. data_2.json.
When I run this in terminal I use the following command:
./api.sh -t token -r rules.json -s data.json > data_2.json
However, I wish to run this command line in Python. Any suggestions are appreciated.
Thanks,

I don't know if it supports python but you can use getopts.
Look here

Does this test.py work:
import subprocess
from subprocess import Popen
path_to_output_file = 'data_2.json'
myoutput = open(path_to_output_file,'w+')
p = Popen(["./api.sh", "-t" , "token", "-r", "rules.json", "-s", "data.json"], stdout=myoutput, stderr=subprocess.PIPE, universal_newlines=True)
output, errors = p.communicate()
You can refer to this for details.

subprocess command execution

What is the best way to execute the below command in Python in a single line?
echo $(readlink /sys/dev/block/$(mountpoint -d /))
Tried using individual os.system(cmd) by separating - "mountpoint -d /" first and taking the output and appending to "readlink /sys/dev/block/${0}".format(out.strip()) and doing an echo works. Tried using subprocess and subprocess.Popen and subprocess.check_output but it raises raise CalledProcessError
cmd = "echo $(readlink /sys/dev/block/$(mountpoint -d /))"

You have to call the subcommand separately. And you can use python methods to read the link:
import subprocess
import os
path = "/"
device = subprocess.run(["mountpoint", "-d", path], stdout=subprocess.PIPE, encoding="utf8").stdout.strip()
link = os.readlink("/sys/dev/block/" + device)
print(link)

You probably want to use something like the following:
cmd = "bash -c 'echo $(readlink /sys/dev/block/$(mountpoint -d /))'"
echo doesn't substitute $() blocks, that's what your shell does, so you have to call the shell. os.system(cmd) should work then.

Python subprocess piping to stdin

I'm trying to use python Popen to achieve what looks like this using the command line.
echo "hello" | docker exec -i $3 sh -c 'cat >/text.txt'
The goal is to pipe the "hello" text into the docker exec command and have it written to the docker container.
I've tried this but can't seem to get it to work.
import subprocess
from subprocess import Popen, PIPE, STDOUT
p = Popen(('docker', 'exec', '-i', 'nginx-ssl', 'sh', '-c', 'cat >/text.txt'), stdin=subprocess.PIPE)
p.stdin.write('Hello')
p.stdin.close()

You need to give stdin the new line also:
p.stdin.write('Hello\n')
That is the same thing even with sys.stdout. You don't need to give print a new line because it does that for you, but any writing to a file that you do manually, you need to include it. You should use p.communicate('Hello') instead, though. It's made for that.

using subprocess module in python to run isql command

I have to run isql command using python.
Currently i'm doing it in this way
ps = subprocess.Popen("""./isql -I /app/sybase/interfaces_global -S %s -U %s -P %s -D %s -s "|" -w 99999 <<EOF
SET NOCOUNT ON
%s
go
EOF""" %(mdbserver,muserid,mpassword,mdatabase,User_Query),stdout=subprocess.PIPE,shell=True,cwd=sybase_path)
But this method is dependent on the /tmp directory of my server because of the here document, everytime when i run it, it creates a tmp file in the /tmp directory and when the /tmp directory is full the script fails to run the Query onto the database.
How can i use the same command with shell=False, So that i can get rid of the here document """ and the temporary file creation.
this doesn't works
ps = subprocess.Popen("./isql","-I","/app/sybase/interfaces_global","-S",mdbserver,"-U",muserid,"-P",mpassword,"-D",mdatabase,"-s","|","-w","99999","\nSET NOCOUNT ON\n",User_Query,"\ngo",stdout=subprocess.PIPE,shell=False,cwd=sybase_path)

You could replace the here-document by setting stdin=PIPE and providing the input as a string using .communicate() method as #Hans Then suggested:
from subprocess import Popen, PIPE
from textwrap import dedent
isql = Popen(['./isql', '-I', '/app/sybase/...',
'-S', mdbserver,
'-U', muserid, ...,
'-w', '99999'], stdin=PIPE, stdout=PIPE, cwd=sybase_path)
output = isql.communicate(dedent("""\
SET NOCOUNT ON
{}
go
""".format(User_Query)))[0]

Check out the subprocess communicate() command. You can use it to send isql commands to the interpreter.

Python subprocess output read error

I have a command which works great at the terminal:
sudo tshark -V -l -i "any" -f 'udp port 4729'
I trying to read the output from my python script:
import subprocess
command = ['tshark', '-V', '-l', '-i', '"any"', '-f', '"udp port 4729"'] # the shell command
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=None)
output, error = process.communicate()
print output
It does not work. Maybe it's some troubles with writing a command in the list.
I receive the error:
gooman#ubuntu:~/workspace/glade_tests/src$ sudo ./main.py
tshark: Lua: Error during loading:
[string "/usr/share/wireshark/init.lua"]:45: dofile has been disabled
Running as user "root" and group "root". This could be dangerous.
Capturing on "any"
tshark: The capture session could not be initiated (No such device exists).
Please check to make sure you have sufficient permissions, and that you have the proper interface or pipe specified.
0 packets captured

Thy this:
import subprocess
command = "sudo tshark -V -l -i "any" -f 'udp port 4729'"
try:
output = subprocess.check_output(command, shell=True)
except subprocess.CalledProcessError as e:
print "An error has been occured", e
raise
print "The subprocess output:", output
Maybe, it will be needed to add stdout=subprocess.PIPE argument.