"shebang /usr/bin/env python" invoking the wrong Python interpreter

Question

What's happening, here?!

$ /usr/bin/env which python /home/dbanas/.local/bin/python $ /home/dbanas/.local/bin/python -V Python 2.7.3 -- EPD_free 7.3-2 (64-bit) $ /usr/bin/env python -V Python 2.4.3

I stumbled upon this, trying to debug one of my Python scripts, which uses a

#! /usr/bin/env python

first line. And I don't understand how it's possible.

Thanks! -db

I did just notice that '~/.local/bin/python' is a link, not an executable. Would that break the '/usr/bin/env ...' flow somehow?

Perhaps, this is a more succinct way to express the fundamental puzzle?:

$ env python -V Python 2.4.3 $ python -V Python 2.7.3 -- EPD_free 7.3-2 (64-bit)

It just keeps getting curioser and curioser:

$ which python /home/dbanas/.local/bin/python $ python -c 'import sys; print sys.executable' /usr/bin/python

the problem doesn't really have to do with shebang but with env running a different version than what which says it should. You might want to clarify the quesiton. What shell are you using? what does env (alone) report for your path? — agentp
– agentp, Commented Mar 26, 2014 at 20:20
@klashxx, I have a space in between '#!' and '/usr/bin/env'. Is that what you meant? Removing that space doesn't seem to change the behavior. — David Banas
– David Banas, Commented Mar 26, 2014 at 20:50
@george, Yes, I agree, the puzzler for me is: "How can '/usr/bin/env which python' yield a different python than the one that '/usr/bin/env python' invokes?" I'm using bash. '"/usr/bin/env | grep '^PATH'" yields: PATH=/apps/lsf/9.1/linux2.6-glibc2.3-x86_64/etc:/apps/lsf/9.1/linux2.6-glibc2.3-x86_64/bin:~/bin:~/.local/bin:... And I have confirmed that a 'python' can NOT be found in any of the directories preceeding '~/.local/bin'. — David Banas
– David Banas, Commented Mar 26, 2014 at 20:57
try type -a python under bash. Also in case you just installed (or moved) the python executable be sure to run a new shell so it sees it on startup. — agentp
– agentp, Commented Mar 26, 2014 at 21:44

jjlin · Accepted Answer · 2014-09-08 19:22:17Z

Most likely what's happening is you don't have your PATH variable exported to the environment. In that case, /usr/bin/env won't have a PATH set, and its execvp call will end up searching a small set of default directories (which typically includes /usr/bin, naturally).

To see this (in bash):

$ export PATH $ declare -p PATH # verify PATH is exported, denoted by the -x declare -x PATH="<my usual path, omitted...>" $ /usr/bin/env python -V # shows my own python build Python 2.7.6 $ export -n PATH # un-export PATH $ declare -p PATH declare -- PATH="<my usual path, omitted...>" $ /usr/bin/env python -V # shows the system (/usr/bin/python) version Python 2.6.6

So, in summary, make sure to export PATH somewhere in your shell dotfiles.

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