When I run in my Ubuntu terminal:
sudo dd if=/dev/sda of=~/file bs=8k count=200k; rm -f ~/file
it works fine.
If I run it through Pythons subprocess.Popen():
output, err = subprocess.Popen(['sudo', 'dd', 'if=/dev/' + disk, 'of=~/disk_benchmark_file', 'bs=8k', 'count=200k'], stderr=subprocess.PIPE).communicate()
print err
it doesn't work. The Error I get is:
dd: failed to open '~/disk_benchmark_file': No such file or directory
If I change in the Popen() call the tilde ~ to /home/user, then it works!
Why is it like that? And more important to me: How can I make it work? I don't know what the user name will be in production.
You need to wrap those pathnames with os.path.expanduser():
>>> import os
>>> os.path.expanduser('~/disk_benchmark_file')
'/home/dan/disk_benchmark_file'
In your code the occurrence of:
['sudo', 'dd', 'if=/dev/' + disk, 'of=~/disk_benchmark_file', 'bs=8k', 'count=200k']
should be replaced with:
['sudo', 'dd', 'if=/dev/' + disk, 'of=' + os.path.expanduser('~/disk_benchmark_file'), 'bs=8k', 'count=200k']