[ros-users] [Ros-developers] suggest new ros shebang command

[William Woodall]

+1

I wonder if this could also be used to control which version of Python you
are using without changing the paths and such.  I have been working on
making ros, ros_comm, and common_msgs more Python 2/3 portable because of
MORSE, which uses Blender, which requires Python3.  I had considered setting
something like env['ROS_PYTHON'] and replacing the #!/usr/bin/env python
lines with something like ros-shebang that would select python executables
and paths based on the environment variable.  This isn't something I see
people doing often, but it might be a use case to consider when designing
this tool.  There might also be a better/existing way of doing what I am
talking about, but I am just not aware of it.

Looks good,

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
William Woodall
Graduate Software Engineering
Auburn University
w at auburn.edu
wjwwood at gmail.com
williamjwoodall.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



On Wed, Aug 10, 2011 at 11:21 AM, Ken Conley <kwc at willowgarage.com> wrote:

> +1
>
> If shorter names are being debated, I offer 'rosbang'.  The placement
> of the hyphen in ros-shebang doesn't quite feel like a ros command
> name.
>
> I should also note that part of this discussion also includes what
> distributions ros-shebang should be included in, i.e. should it be
> backported to diamondback, sneak in through the electric freeze,
> etc...
>
> The hashbang spec has definitely been an impediment for having a good
> ease-of-use with rosh, so I support at least having this in ROS
> Electric.  I'm indifferent to ROS Diamondback as my development is
> always focused on the latest-and-greatest release.
>
>  - Ken
>
> On Tue, Aug 9, 2011 at 2:40 PM, Thibault Kruse <kruset at in.tum.de> wrote:
> > Hi,
> >
> > I would like to make a suggestion.
> >
> > I want to add a command (called ros-shebang for now) to ros/bin that runs
> > script files by invoking a second shebang line.
> >
> > This allows invoking script interpreters with #! and passing additional
> > arguments, as well as invoking interpreters that live in ROS packages.
> >
> > My stake is calling an interpreter for roslisp scripting. However a
> > similar concern is invoking of rosh plugins, see
> > http://www.ros.org/wiki/rosh/Overview/Roshlets
> >
> > Example for rosh:
> > #! /usr/bin/env ros-shebang
> > #! /usr/bin/env rosrun rosh rosh rosh/echolet.py
> > --plugins=rosh_common,rosh_geometry
> >
> > Example for roslisp:
> >
> > #! /usr/bin/env ros-shebang
> > ;; /usr/bin/env rosrun sbcl run-sbcl.sh --script
> >
> > One less known alternative is to use other directives to declare the
> > script interpreter than #!, (in case you wonder, for lisp, #| and ":";
> > work) however this does not work with python subprocess.Popen, which
> means
> > roslaunch and rostest would fail to run scripts like that (except using
> > shell=True, but this is strongly discouraged for security and portability
> > reasons).
> >
> > Alternatives:
> > - A modification to roslaunch syntax to allow forcing shell=true
> >
> > - an executable in ros/bin that executes roslisp scripts, such that we
> > could write:
> > #! /usr/bin/env ros-run-roslisp-script
> >
> > - A required fixed installation of our lisp implementation, or some
> custom
> > made variant of /usr/bin/env
> >
> >
> > I wrote a ros-shebang script in python that works, which is no more magic
> > than reading the second line and calling python execvp on it (minus the
> > first two symbols).
> >
> > If a new command were introduced to ros/bin, this would affect more
> people
> > than those working with roslisp, so opinions should be heard. There is no
> > urgency to this, roslisp works fine as it is without offering comfortable
> > scripting, just as rosh works fine by loading plugins after the shebang
> > line.
> >
> > Not sure if there are other scripting interpreter usages with similar
> > issues in ROS (Java, Lua, Javascript, ...).
> >
> > Thoughts?
> >
> >  Thibault
> >
> > _______________________________________________
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> >
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