> On 27/05/14 21:01, Adam Gold wrote:
>
>> "dd if=/home/adam/1 bs=4k conv=noerror,notrunc,sync | pbzip2 > 1.img.bz2"
>>
>> The first thing I do is break it into two assignments
>
> And that's the start of the problem because it should be three:
> The first command, the second command and the output file.
>
>> ddIf = shlex.split("dd if=/home/adam/1 bs=4k conv=noerror,notrunc,sync")
>> compress = shlex.split("pbzip2 > /home/adam/1.img.bz2")
>
> compress = "pbzip2"
> outfile = open('/home/adam/1.img.bz2','w')
>
> The redirection symbol is not something subprocess can
> use as an argument.
>
>> p1 = subprocess.Popen(ddIf, stdout=subprocess.PIPE)
>> p2 = subprocess.Popen(compress, stdin=p1.stdout, stdout=subprocess.PIPE)
>
> Use the output file here.
>
> p2 = subprocess.Popen(compress, stdin=p1.stdout, stdout=outfile)
>
>
>> I think that the '>' redirect needs to be dealt with using the
>> subprocess module as well but I can't quite put the pieces together.
>> I'd appreciate any guidance. Thanks.
>
> Alternatively read the output into a variable using communicate but then
> write it out to the file manually at the end.
>
> [You might also be able to use shell=TRUE but that introduces other
> issues. But I don't know whether using shell includes redirection.]
>
Thanks Alan, yes, I realise now I needed a third assignment to make this
work.
I actually had an exchange with subscriber 'eryksun' yesterday who did a
great job of pointing me in the right direction. As a bit of a noob, I
think I replied to the individual rather than the list, hence it doesn't
seem to be in the thread. For the benefit of the archives I append
below eryksun's initial (there was a bit of follow up but nothing too
important) reply to me.
=====================================
Send p2's stdout to a file:
import subprocess
import shlex
ddIf = shlex.split("dd if=/home/adam/1 bs=4k "
"conv=noerror,notrunc,sync")
compress = "pbzip2"
filename = "/home/adam/1.img.bz2"
p1 = subprocess.Popen(ddIf, stdout=subprocess.PIPE)
with p1.stdout as fin, open(filename, "w") as fout:
p2 = subprocess.Popen(compress, stdin=fin, stdout=fout)
ret1 = p1.wait()
ret2 = p2.wait()
Does this work?
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