#######################
Linux
#######################

output to screen, stderr and text file
***************************************

Output to both stderr and displayed at terminal/console::

    $ command 2>&1 | tee logfile.txt

    Chart for StdOut/StdErr

               || visible in terminal ||   visible in file   || existing
      Syntax  ||  StdOut  |  StdErr  ||  StdOut  |  StdErr  ||   file
    ==========++==========+==========++==========+==========++===========
        >     ||    no    |   yes    ||   yes    |    no    || overwrite
        >>    ||    no    |   yes    ||   yes    |    no    ||  append
              ||          |          ||          |          ||
       2>     ||   yes    |    no    ||    no    |   yes    || overwrite
       2>>    ||   yes    |    no    ||    no    |   yes    ||  append
              ||          |          ||          |          ||
       &>     ||    no    |    no    ||   yes    |   yes    || overwrite
       &>>    ||    no    |    no    ||   yes    |   yes    ||  append
              ||          |          ||          |          ||
     | tee    ||   yes    |   yes    ||   yes    |    no    || overwrite
     | tee -a ||   yes    |   yes    ||   yes    |    no    ||  append
              ||          |          ||          |          ||
     n.e. (*) ||   yes    |   yes    ||    no    |   yes    || overwrite
     n.e. (*) ||   yes    |   yes    ||    no    |   yes    ||  append
              ||          |          ||          |          ||
    |& tee    ||   yes    |   yes    ||   yes    |   yes    || overwrite
    |& tee -a ||   yes    |   yes    ||   yes    |   yes    ||  append


n.e -> won't fit in this space


Upgrade Python in Ubuntu 18+
****************************

::

    # check version
    $ python3 --version # or
    $ python --version
    # install python 3.8
    $ sudo apt update -y
    $ sudo apt install python3.7
    # add python 3.7 and python 3.8 to update-alternatives
    $ sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.7 1
    $ sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.8 2
    # update python3 to point to python 3.8
    $ sudo update-alternatives --config python3
    $ sudo update-alternatives --config python3
    # You will get the following output
    There are 2 choices for the alternative python3 (providing /usr/bin/python3).

      Selection    Path                Priority   Status
    ------------------------------------------------------------
    * 0            /usr/bin/python3.7   1         auto mode
      1            /usr/bin/python3.7   1         manual mode
      2            /usr/bin/python3.8   2         manual mode

    Press <enter> to keep the current choice[*], or type selection number:
    # update by pressing 2

Alternative update choice, create a new symlink to python 3.8::

    $ sudo rm /usr/bin/python3
    $ sudo ln -s python3.8 /usr/bin/python3

Thanks to '<https://dev.to/serhatteker/how-to-upgrade-to-python-3-7-on-ubuntu-18-04-18-10-5hab>'_