Using a zipped file as a shell stdin

Question

I'm trying to write a short script that will recover a repository. The backup script generates dump files that are gzipped.

To apply a dump I need to call this command:

svnadmin load < myfile

but since myfile is a gzipped one, I need to unzip it for the command to work.

Now here comes my question, is the command on top same as

subprocess.call(['svnadmin','load', myfilecontents])

This way I will avoid the need to unzip the file, to a temporary location. or should I be using

subprocess.call(['svnadmin','load'],stdin=gzip.open(myfile))

zcat myfile | svnadmin load is more likely to be the command you want to model with subprocess... (or gzip -dc, if for some reason, your distro of choice doesn't provide zcat) — twalberg
– twalberg, Commented Nov 12, 2013 at 19:55

Robᵩ · Accepted Answer · 2013-11-12 20:02:33Z

You can't point stdin at a GzipFile, but you can copy the data yourself

In [5]: cmd=subprocess.Popen(["od", "-cx"], stdin=subprocess.PIPE) In [6]: data=gzip.open("/tmp/hello.gz") In [8]: cmd.stdin.write(data.read()) In [9]: cmd.stdin.close() 0000000 h i \n 6968 000a 0000003

Alternatively, you could use Popen.communicate():

In [11]: cmd=subprocess.Popen(["od", "-cx"], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE) In [12]: data=gzip.open("/tmp/hello.gz") In [13]: cmd.communicate(data.read()) Out[13]: ('0000000 h i \\n\n 6968 000a\n0000003\n', '')

Agreed, and if twalberg creates an answer based on his comment, I'd probably upvote it.

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