In python the first line of the script should be
#!/usr/bin/env/python{3}
Is there a way to do:
if python:
#!/usr/bin/env/python
else:
#!/usr/bin/env/python3
EDIT:
Running python in RHEL7 bring up python-2.7.5 (default).
Only running python3 will execute python3-3.6.8 on my RHEL7.
I can't say I recommend this at all, but it does work:
#!/bin/bash
_=""""
if [[ -x '/usr/bin/python3' ]]
then
exec /usr/bin/python3 "$0" "$@"
elif [[ -x '/usr/bin/python' ]]
then
exec /usr/bin/python "$0" "$@"
else
echo "No python available"
exit 1
fi
"""
import sys
sys.stdout.write("you made it\n")
Can't do from __future__ import print_function because it has to be the first line of python.
Principles here are to use bash to do the executable detection but also make it valid python so you can just re-execute with the python interpreter on the same file.
None of those are correct. The correct command is /usr/bin/env and the argument to that, after a space, is the name of the actual interpreter you want it to look up.
Your question is a bit of a "turtles all the way down" problem. You have to know what command you want to run. You could of course create yet another tool and call it something like py3orpy but then you need to know that that exists in the PATH before you try to ask env to find it.
I would expect us to eventually converge on python; if you can't rely on that, perhaps the least error-prone solution is to figure out what's correct for the target system at installation time, and have the installer write a correct shebang. Or just install a symlink /usr/local/bin/python3 if it doesn't exist already, and hardcode #!/usr/bin/env python3 everywhere.
python3, there you have it.
In python the first line of the script should be #!/usr/bin/env/python{3}? As far as I'm concerned there is nothing like that.pythonscript, not aPerlone or ashellone.bash/whatever other unix shell thing. It tells the shell what interpreter to use, it's called a shebang (short for hash#bang!). It's only a thing for unix/linux/etc. systems, nothing to do with python at all.pythonandpython3where people has to work with both on 2 different environments.sixfor compatibility between python2 and python3. See: six.readthedocs.io