[Distutils] [PATCH] Handling of scripts / substitution of python executable path

[Hans Meine]

Hi!

For a long time, I have been annoyed by distutils behavior concerning 
"scripts":  I always put 
  #!/usr/bin/env python
into the first line in order to let the incredibly useful "env" program start 
the right python version.

I know that it is quite evil to hardcode /usr/bin/python 
or /usr/local/bin/python; I have seen dozens of #! hacks for finding e.g. 
perl, and I was delighted to find /usr/bin/env, which solves the problem once 
and for all.  (And yes - it is always in /usr/bin/! ;-) )

Now distutils tries to be intelligent and "destroys" my nice #! lines, which 
can be quite evil in complex setups, e.g. when you share your home directory 
via NFS (or rsync/unison) between several environments with different python 
installations.  Furthermore, we are using the "module" system here at our 
university, so that I can dynamically choose between half a dozen python 
versions ("module" manages your PATH variables).  Replacing the python path 
turns nice, pure python scrips into platform-specific programs as you can see 
here:

meine at kogspc12:~ head -n1 ~/vigra/interactive/build/scripts-2.4/pyterm
#!/software/python-2.4.4/SuSE-9.0/bin/python

Note the SuSE-9.0 exec-prefix in the path; we are using several Linux and 
Solaris versions here:

meine at kogspc12:~/tmp/vi3build -> ls -1 /software/python-2.4.4/*/bin/python
/software/python-2.4.4/SuSE-10.0/bin/python*
/software/python-2.4.4/SuSE-9.0/bin/python*
/software/python-2.4.4/SunOS-5.8/bin/python*

I see that distutils as it is now does the right thing
* on Windows systems,
* on any system where /usr/bin/env is missing, or
* when the source file has a #! with a broken path.

What I propose is a minimal invasive change which keeps /usr/bin/env iff it is 
in the #! line *and* exists on the current system.  (A more brave change 
would be to always use /usr/bin/env if it exists, but I think that is a topic 
open for discussion.)  Attached you'll find a patch which implements this; I 
did not yet update tests/test_build_scripts.py however.

Comments?

Ciao, /  /
     /--/
    /  / ANS
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