Use of a configuration file

[CharlesGodwin]

When starting a tool from the command line or in a shell script the need to define all options and then enter them can be problematic. A common solution is to create a configuration fie with all the settings defined. I have studied the possible solutions available and think I have a workable solution.

My choices where:

• Use a python configuration parser. This would add a separate method of defining options. For many users this may be over complicated.
• Use a YAML configuration file. This too adds complexity and there doesn't seem to be much consensus about what is the right or wrong architecture. Again, this is a complex solution for a simple problem.
• Use environmental variables. Users could create a simple file with set statements, such as
  DEVICE="/dev/ttyUSB0" and then run this file as you execute the command. This failed for these reasons.
  • It is very rigid and doesn't have much flexibility
  • It could prove awkward to use
  • It would also add another layer of complexity to the parsing of options

I had decided on the following:
Use the optional file parameter built into python's argparse tool. The programs are all ready using this tool to parse the command line options so it's easy to create an options file, containing lines similar to the command line and direct the program to use it. For example magdump @pymagnum.opt would invoke magdump and the options would be read from a file named pymagnum.opt. Here is what a default option file would look like. The # character is the beginning of a comment and are stripped.

# Alter these to suit
--device /dev/ttyUSB0
--interval 60
--packets 50
--timeout 0.005
# Remove # to enable the following
#--verbose
#--trace
#--nocleanup
#
# Following for magserver example
--port 17223
--listen ALL
#
# Following for mqttlogger
--broker localhost:1883
--topic magnum/

This solution is being prepared for use in version 2.0 unless I get convincing feedback