How can specifying the absolute path $ /usr/bin/python have a different result than $ python when its aliased to the same path?

Question

I'm trying to make PyLucene which has a required dependency JCC. (JCC is a code generator for calling Java from Python.)

Note: OS is Mac OS X 10.7.4.

The included make script runs:

$ /usr/bin/python -m jcc

output:

/usr/bin/python: No module named jcc

but running the following is successful:

$ python -m jcc

Even though python points to /usr/bin/python:

$ whereis python

output:

/usr/bin/python

When the python alias points to /usr/bin/python, how can these results be different?

Answer 1

Try running python --version on both and see if they are the same.

Answer 2

Your problem might be the hash table. Bash keeps a table of remembered commands - it does not search $PATH each time. If python was called before the alias was setup then the hash table will get used. My understanding though is that aliases are expanded before the hash table is searched, but the man pages are not clear on that.

Check this by listing the hash table using the hash command. Reset the hash table using hash -d python.

However, I note that you are using make, although your example is command-line. Aliases are not inherited (by default) by child processes, and it would probably be a support nightmare if it did. So make is not using your alias.