piping with subprocess
Peter Otten
__peter__ at web.de
Sat Feb 1 07:54:09 EST 2014
Rick Dooling wrote:
> I spent half a day trying to convert this bash script (on Mac)
>
> textutil -convert html $1 -stdout | pandoc -f html -t markdown -o $2
>
> into Python using subprocess pipes.
>
> It works if I save the above into a shell script called convert.sh and
> then do
>
> subprocess.check_call(["convert.sh", file, markdown_file])
>
> where file and markdown_file are variables.
>
> But otherwise my piping attempts fail.
It is always a good idea to post your "best effort" failed attempt, if only
to give us an idea of your level of expertise.
> Could someone show me how to pipe in subprocess. Yes, I've read the doc,
> especially
>
> http://docs.python.org/2/library/subprocess.html#replacing-shell-pipeline
>
> But I'm a feeble hobbyist, not a computer scientist.
Try to convert the example from the above page
"""
output=`dmesg | grep hda`
# becomes
p1 = Popen(["dmesg"], stdout=PIPE)
p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
p1.stdout.close() # Allow p1 to receive a SIGPIPE if p2 exits.
output = p2.communicate()[0]
"""
to your usecase. Namely, replace
["dmesg"] --> ["textutil", "-convert", "html", infile, "-stdout"]
["grep", "hda"] --> ["pandoc", "-f", "html", "-t", "marktown", "-o",
outfile]
Don't forget to set
infile = ...
outfile = ...
to filenames (with absolute paths, to avoid one source of error).
If that doesn't work post the code you wrote along with the error messages.
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