[Python-Dev] [PEPs] Support the /usr/bin/python2 symlink upstream

[Toshio Kuratomi]

On Tue, Mar 08, 2011 at 06:43:19PM -0800, Glenn Linderman wrote:
> On 3/8/2011 12:02 PM, Terry Reedy wrote:
> 
>     On 3/7/2011 9:31 PM, Reliable Domains wrote:
> 
> 
>         The launcher need not be called "python.exe", and maybe it would be
>         better called #@launcher.exe (or similar, depending on its exact
>         function details).
> 
> 
>     I do not know that the '#@' part is about, but pygo would be short and
>     expressive.
> 
> 
> 
> If my proposal to make a line starting with #@ to be used instead of the Unix
> #! (#@ could be on the first or second line, to allow cross-platform scripts to
> use both, and Windows only scripts to not have #!
>
You'd need to allow for it to be on the third line as well.  pep-0263
has already taken the second line if it's in a script that has a Unix
shebang.


> ), then #@launcher.exe (and #
> @launcherw.exe I suppose) would reflect the functionality of the launcher,
> which need not be tightly tied to Python, if it uses a separate line.  But the
> launcher should probably not be the thing invoked from the command line, only
> implicitly when running scripts by naming them as the first thing on the
> command line.
> 
> I'm of the opinion that attempting to parse a Unix #! line, and intuit what
> would be the equivalent on Windows is unnecessarily complex and error prone,
> and assumes that the variant systems are configured using the same guidelines
> (which the Python community may espouse, but may not be followed by all
> distributions, sysadmins, or users).
>
I do not have a Windows system so I don't have a horse in this race but if
the argument is to avoid complexity, be careful that your proposed solution
isn't more complex than what you're avoiding.  ie::

> Now that I've had this idea, one might want to create other "2nd character"
> codes after the Unix #! line... one could have
> 
> #! Unix command processor
> #@ Windows command processor
> #$ OS/2 command processor
> #% Alternate Windows command processor.
> 
> One could even port it to Unix:
> 
> #!/usr/bin/#@launcher
> #@c:\python2.6\python.exe
> #^/usr/bin/python2.5
> #&/usr/bin/mono/IronPython2.6 for .NET 4.0/ipy.exe
> #  I made up the line above, having no knowledge of Mono, but I think you get
> the idea
> 
> Choice of command line would be an environment variable, I suppose, that the
> launcher would look at, or if none, then a system-specific default.  It would
> have to search forward in the file until it finds the appropriate prefix or a
> line not starting with #, or starting with "# " or "##", at which point it
> would give up.
> 
-Toshio
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