Alternatives use notes, alternatives notes

Alternatives use notes, alternatives notes

The X64 ora23 X64 system has multiple versions of python. The default version is python2.7.

$ ls -l /usr/bin/python*lrwxrwxrwx. 1 root root    24 Mar 26 15:49 /usr/bin/python -> /usr/bin/python2lrwxrwxrwx. 1 root root     9 Jun 20  2016 /usr/bin/python2 -> python2.7-rwxr-xr-x. 1 root root  7088 Jun 20  2016 /usr/bin/python2.7lrwxrwxrwx. 1 root root     9 Jun 29  2015 /usr/bin/python3 -> python3.4-rwxr-xr-x. 2 root root 11184 Jun 29  2015 /usr/bin/python3.4-rwxr-xr-x. 2 root root 11184 Jun 29  2015 /usr/bin/python3.4m-rwxr-xr-x. 1 root root   308 Jun 19  2015 /usr/bin/python3-chardetect-rwxr-xr-x. 1 root root   301 Sep 28  2015 /usr/bin/python3-coverage-rwxr-xr-x. 1 root root   301 Jun 19  2015 /usr/bin/python3-mako-render-rwxr-xr-x. 1 root root    43 Jun 19  2015 /usr/bin/python3-pyinotify

Now you want to switch to the default version of python3.4. Use the alternatives command and use alternatives -- display python to find that python is not in the management list of alternatives. Add python of different versions to alternatives and use usage: alternatives -- install <link> <name> <path> <priority>

$ alternatives --install /usr/bin/python python /usr/bin/python2.7 1$ alternatives --install /usr/bin/python python /usr/bin/python3.4 2

View alternatives -- display python

$ alternatives --display pythonpython - status is auto. link currently points to /usr/bin/python3.4/usr/bin/python2.7 - priority 1/usr/bin/python3.4 - priority 2Current `best' version is /usr/bin/python3.4.

We can see that the alternatives point to python3.4.

$ ls -l /usr/bin/python*lrwxrwxrwx. 1 root root    24 Mar 26 15:49 /usr/bin/python -> /etc/alternatives/pythonlrwxrwxrwx. 1 root root     9 Jun 20  2016 /usr/bin/python2 -> python2.7-rwxr-xr-x. 1 root root  7088 Jun 20  2016 /usr/bin/python2.7lrwxrwxrwx. 1 root root     9 Jun 29  2015 /usr/bin/python3 -> python3.4-rwxr-xr-x. 2 root root 11184 Jun 29  2015 /usr/bin/python3.4-rwxr-xr-x. 2 root root 11184 Jun 29  2015 /usr/bin/python3.4m-rwxr-xr-x. 1 root root   308 Jun 19  2015 /usr/bin/python3-chardetect-rwxr-xr-x. 1 root root   301 Sep 28  2015 /usr/bin/python3-coverage-rwxr-xr-x. 1 root root   301 Jun 19  2015 /usr/bin/python3-mako-render-rwxr-xr-x. 1 root root    43 Jun 19  2015 /usr/bin/python3-pyinotify

　　

$ ls -l /etc/alternatives/python lrwxrwxrwx. 1 root root 18 Mar 26 15:49 /etc/alternatives/python -> /usr/bin/python3.4

　　

Note:

Update-alternatives and alternatives are the same commands.

$ ls -l /usr/sbin/update-alternatives lrwxrwxrwx. 1 root root 12 Oct  2  2015 /usr/sbin/update-alternatives -> alternatives

[1] https://linuxconfig.org/how-to-change-from-default-to-alternative-python-version-on-debian-linux