   Installing and running Linux binary distribution of Obit

NOTE: Python 3 upgrade.
   As of version 610 (Nov. 2019), the Obit python routines should work
with either python version 2.7 or python 3, whichever is run using
command "python" (or /usr/bin/python). Part of this upgrade is to
require some python 3 features (e.g. parentheses in print statements)
in existing scripts, even using python 2.7.  This was a major revision
of the python interface and it no longer works with older versions of
python.  
   Further, due to gross incompetence on the part of Python Inc., this 
binary distribution will only work in python 2.7 built with the same
variant of PyUnicode (UCS4).  An attempt to run with a python2.7 built
with UCS2 will fail with a complaint about missing
PyUnicodeUCS4_AsUTF8String.  python 3 should not have this problem.
There is a script ObitTalk3 which attempt to start ObitTalk using
python3 if it is in your path with the name "python3".

Python 3 traumas
   Python 3 has removed or seriously changes many of the most popular
scripting features of python which may require modification of your
existing scripts.   Among others these are:
 1) print statements need parentheses, e.g. print ("something")
 2) function execfile has been deleted.  
   exec(open('filename.py').read()) seems to work but is not the
   recommended way by Python Inc.
 3) the integer "/" operator now promotes the arguments to float, to
   get proper (integer) results use "//"
 4) strings were removed and replaced with some variant of PyUnicode,
   this may not bite you but see above.
 5) int data types are now long (64 bits)
 6) scoping rules have changes and more variables need to be
   explicitly declares "global".
 7) to upgrade to python 3 features using a python 2.7 add the lines
from __future__ import absolute_import
from __future__ import print_function
   to your script.  Sadly the from __future__ import feature does not
   work for stock market reports.

   The distribution contains a version of _Obit.so,
 _Obit.cpython-36m-x86_64-linux-gnu.so which is built explicitly for
 python3.6 but sees to work for later versions as well.  You may have
 link this file to _Obit.so in the same directory.

1) Unpack the distribution tarball in the directory in which you wish
   to install it; e.g.
 > mv obit-distro-1.1.637.tar.gz /home/mydir/obitinstall
 > cd /home/mydir/obitinstall
 > tar zxf obit-distro-1.1.637.tar.gz

2) Add the top level distribution to your path:
 > setenv PATH "/home/mydir/obitinstall/obit-distro-1.1.637/bin:$PATH"
if you use tcsh or, for bash
 > PATH="/home/mydir/obitinstall/obit-distro-1.1.637/bin:$PATH"; export PATH
You may wish to add these to your .cshrc or .profile login files.

3) ObitTalk is the python based user interface, documentation is in
doc/ObitTalk.pdf.

4) Additional customization is possible using the python file
dot.obitrc.py renamed to .obitrc.py and placed in your home directory
($HOME) or in the working directory from which you run ObitTalk.
This can be used to define the location of AIPS and AIPS data
directories as well as FITS data directories.  Alternatively, the
standard AIPS startup scripts will define the AIPS environment.

5) If the host has a version of python in /usr/bin/python, the
distributed versions of the scripts will use it.  Otherwise 
/home/mydir/obitinstall/obit-distro-1.1.637/lib/obit/bin/ObitTalk 
needs to be modified at the end to use an available python.

   NOTE: If you want to run tasks from 31DEC17 or later AIPS, you'll
need to copy the libraries (lib*.so) from
$AIPS_ROOT/$AIPS_VERSION/LNX64/LIBR/INTELCMP/ to
obit-distro-1.1.637/lib/.
