What are the rules for launch-prefix?

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RLException: Invalid roslaunch XML syntax: not well-formed (invalid token):

The particular error you show just tells us that you have something in that attribute which is not valid XML.

As .launch files are XML, you need to ensure that whatever you have in the launch-prefix attribute is valid XML as well. This means: no special characters, no ", no &, etc.

You'll have to escape/encode those characters before putting them in that attribute. I 'd suggest looking up some sites about XML and entity encoding.

What are the rules for launch-prefix?

Ignoring the "valid XML" aspect, here are some guidelines:

• it needs to be something that can actually be executed
• it needs to be something which does not interfere with roslaunch's process monitoring (or: if it would interfere you'll just run into problems when trying to shutdown your launch session)
• it needs to be able to process the "rest of the command line" (ie: path and name of node binary, any additional args to the node binary)

there may be more, perhaps other board members can contribute.