Python管道模块如何做“猫”

Question

I am trying to do this in python:

cat foo | ssh me@xxxx hadoop fs -put - bar/foo

I have originally tried a check_call:

foo = 'foo'
subprocess.check_call(['cat', foo, '|','ssh',os.environ['USER']+'@'+hadoopGateway,'hadoop','fs','-put', '-', inputArgs.targetDir+'/'+foo])

which produces the error:

cat: invalid option -- 'p'

I have looked at the python pipes module documentation and played around with it in the shell, but I do not understand how to kick it off without an output file, like the example.

>>> t = pipes.Template()
>>> t.prepend('cat foo', '.-')
>>> t.append('hadoop fs -put - bar/foo', '-.') # what next

Clearly I am missing something.

Answer 1

You don't need cat or a pipeline for this; all you need is to provide the file as standard input to the ssh command. In shell, that would be

ssh ${USER}@${hadoopGateway} hadoop fs -put - ${targetDir}/foo < foo

and with the Python subprocess module it's only a tiny bit more involved:

foo='foo'
subprocess.check_call(['ssh',
                       os.environ['USER']+'@'+hadoopGateway,
                       'hadoop', 'fs', '-put', '-', inputArgs.targetDir+'/'+foo],
                      stdin=open(foo, 'r'))