Problem passing bash output to a python script

Question

I'm fairly new to programming and I searched the internet for a way to pass bash output to a Python script.

I came up with this in bash.

XAS_SVN=`svn info` 
ssh hudson@test "python/runtests.py $XAS_SVN"

And this in python.

import sys
print sys.argv[1]

When I echo $SVN_INFO I get the result.

Path: . URL: //svn/rnd-projects/testing/python Repository Root: //svn/rnd-projects Repository UUID: d07d5450-0a36-4e07-90d2-9411ff75afe9 Revision: 140 Node Kind: directory Schedule: normal Last Changed Author: Roy van der Valk Last Changed Rev: 140 Last Changed Date: 2009年06月09日 14:13:29 +0200 (2009年6月09日)

However the python script just prints the following.

Path:

Why is this and how can I solve this? I the $SVN_INFO variable not of string type?

I know about the subprocess module and the Popen function, but I don't think this is a solution since the python script runs on another server.

• tonfa: Why was af's answer validated, it doesn't actually work, you can't expand a variable inside single quotes (try `echo '$PATH').

Answer 1

Since you have spaces in the variable, you need to escape them or read all the arguments in your script:

print ' '.join(sys.argv[1:])

But it might be better to use stdin/stdout to communicate, especially if there can be some characters susceptible to be interpreted by the shell in the output (like "`$'). In the python script do:

for l in sys.stdin:
 sys.stdout.write(l)

and in shell:

svn info | ssh hudson@test python/runtests.py

Answer 2

Yes, you need to put in quotes your input to python/runtest.py because otherwise argv[1] gets it only up to the first space. Like this:

ssh hudson@test "python/runtest.py \"$XAS_SVN\""

• tonfa: Did you test this? If you use single quotes, the variable XAS_SVN won't be expanded.
• af.: Yes, that's true. I had a little mix-up when testing my un-edited answer, which was like it is now. I tested it with different shell and it handled the quotes differently. My bad.
• Roy van der Valk: First it didn't work, but after your edit it works perfectly, thanks!