Using dd command through Python's subprocess module

Question

Through Python's subprocess module, I'm trying to capture the output of the dd command. Here's the snippet of code:

r = subprocess.check_output(['dd', 'if=/Users/jason/Desktop/test.cpp', 'of=/Users/jason/Desktop/test.out'])

however, when I do something like

print r

I get a blank line.

Is there a way to capture the output of the dd command into some sort of data structure so that I can access it later?

What I essentially want is to have the output below be stored into a list so that I can later do operations on say the number of bytes.

1+0 records in
1+0 records out
4096 bytes transferred in 0.000409 secs (10011579 bytes/sec)

Answer 1

dd does not output anything to stdout, so your result is correct. However, it does output to stderr. Pass in stderr=subprocess.STDOUT to get the stderr output:

>>> o = subprocess.check_output(
    ['dd', 'if=/etc/resolv.conf', 'of=r'], stderr=subprocess.STDOUT)
>>> print(o)
b'0+1 records in\n0+1 records out\n110 bytes (110 B) copied, 0.00019216 s, 572 kB/s\n'