At 9:41 PM -0600 12/16/12, Ryan Schmidt wrote:
On Dec 16, 2012, at 14:49, Craig Treleaven wrote:
At 12:10 AM +1100 12/17/12, Joshua Root wrote:
On 2012-12-16 19:46 , vincent habchi wrote:
Some scripts of a port I'm trying to set up use #!/usr/bin/env
python, which seem to always point to Apple's python. Which
environment variable have I to change so that 'env' will return a
MacPorts python instead?
There is no environment variable that will help here; 'python' is not
guaranteed to be present in ${prefix}/bin.
The reason /usr/bin/env is used in the shebang line here is that the
interpreter for a script must be an absolute path, but the author
doesn't know where python will be on the user's system. The env command
is for altering the environment, but is used without setting any
variables, and is thus a noop that gets around the absolute path
requirement. Only PATH has any effect on which python is found.
For my edification...I see this all the time with Python but never
Perl. Is there some reason the former needs it and the latter
doesn't? Do other scripting languages require the env 'trick'?
We usually want to use only MacPorts software, but this is not
enforced for little utilities like awk, sed and grep, and perl
sometimes fits into that category too. For one thing, perl has been
around for such a long time that every version of OS X MacPorts runs
on contains a sufficiently-new version of perl. The exception, and
the case when you definitely should depend on and ensure you're
executing a specific MacPorts perl, is when the script requires the
use of perl modules.
perl is also unusual compared to the other multi-version scripting
languages in MacPorts in that we actually do have a port that
provides ${prefix}/bin/perl. That's an aberration, not something we
want to emulate elsewhere, and it should probably be changed:
https://trac.macports.org/ticket/29763
Sorry, Ryan, that wasn't what I was trying to ask about. I
understand about making sure that a port-specified versions of perl
and python get used. (Lord knows my mythtv-core.25 port would be a
lot shorter if that wasn't required!)
I was just curious why a lot of the Python scripts I've run across
use the env trick. Sounds like it was a workaround as the path to
the python executable was unpredictable on some systems.
Craig
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