Develop Reference

How to change newline to enter in commands run by Popen?

I want to change password through python script.
import subprocess
cmd = 'echo -e "newpass1\nnewpass1" | passwd root'
with subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE) as p:
print(p.stderr.read(4096))
Result of this command is error: "Passwords do not match".
Why this command is working in my shell and not working in python script?

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.

Using $PWD with subprocess.Popen() results in a Docker error, works from shell

I want to run a docker command from python using the subprocess Popen:
proc = subprocess.Popen(
shlex.split(r'docker run -v $PWD:/data blang/latex pdflatex main.tex'),
cwd=temp_dir, shell=False, stdout=subprocess.PIPE,
stdin=subprocess.PIPE, stderr=subprocess.PIPE)
proc.communicate()
While the command from the terminal works perfect, this returns:
(b'',
b'docker: Error response from daemon: create $PWD: "$PWD" includes invalid characters for a local volume name, only "[a-zA-Z0-9][a-zA-Z0-9_.-]" are allowed.\nSee \'docker run --help\'.\n')

"$PWD" is a shell expansion. If you don't have a shell (as with shell=False), it doesn't get expanded.
'%s:/data' % os.getcwd() is a Python expression which will have the same result as "$PWD:/data" in shell. Thus:
import os, subprocess
proc = subprocess.Popen(
['docker', 'run',
'-v', '%s:/data' % os.getcwd(),
'blang/latex', 'pdflatex', 'main.tex'],
cwd=temp_dir, shell=False, stdout=subprocess.PIPE,
stdin=subprocess.PIPE, stderr=subprocess.PIPE)
It's important not to use shlex.split() in this case: If you did, and were in a directory with spaces in its name, each segment of that directory would become a separate argument.

Running rsync from python subprocess in windows

I need to run rsync from Python 2.7 app in windows 7 x64 (using cwRsync 5.5.0).
Everything works fine from command line:
set CWRSYNCHOME in env to cwrsync binaries and run following command
rsync.exe "/cygdrive/e/test" test1#192.168.1.14:
But when trying to run same command as python subprocess:
process = subprocess.Popen(['rsync.exe', '/cygdrive/e/test', 'test1#192.168.1.14:'],
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
shell=True,
env={'CWRSYNCHOME': './bin'})
stdout, stderr = process.communicate()
print 'STDOUT:{}\nSTDERR:{}'.format(stdout, stderr)
I get following error in stderr:
rsync: pipe: Operation not permitted (1)
rsync error: error in IPC code (code 14) at pipe.c(59) [sender=3.1.2]
Here is verbose rsync stdout:
FILE_STRUCT_LEN=16, EXTRA_LEN=4
cmd=<NULL> machine=192.168.1.14 user=test1 path=.
cmd[0]=ssh cmd[1]=-l cmd[2]=test1 cmd[3]=192.168.1.14 cmd[4]=rsync cmd[5]=--server cmd[6]=-vvvvve.LsfxC cmd[7]=. cmd[8]=.
opening connection using: ssh -l test1 192.168.1.14 rsync --server -vvvvve.LsfxC . . (9 args)
[sender] _exit_cleanup(code=14, file=pipe.c, line=59): entered
[sender] _exit_cleanup(code=14, file=pipe.c, line=59): about to call exit(14)
Tryed set shell=False and pass command as single line (not cmd and args) - error stil repeats.
What am i doing wrong ?

To get it work, rsync needs to be runned under cygwin's shell:
process = subprocess.Popen(['sh.exe', '-c',
'rsync /cygdrive/e/test test1#192.168.1.14:'],
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
stdin=subprocess.PIPE,
env={'CWRSYNCHOME': '/bin/',
'PATH': '/bin/'})
It's working (there is no ssh athorization in example above).

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.