Question

Let’s imagine we have some script ‘m12’ (I’ve just invented this name) that runs
on Linux computers. If it is situated in your $PATH, you can easily run it
from the console like this:

m12 

It will work with the default parameters. But you can customize the work of
this script by running it something like:

m12 --enable_feature --select=3

It is great and it will work. But I want to create a config file ~/.m12rc so I
will not need to specify --enable_feature --select=3 every time I run it.
It can be easily done.

The difficult part is starting here.

So, I have ~/.m12rc config file, but I what to start m12 without parameters that
are stored in that config file. What is the Unix way to do this? Should I run
script like this:

m12 --ignore_config

or there is better solution?

Next. Let’s imagine I have a config file ~/.m12rc and I want some parameters from that
file, but want to change them a bit. How should I run the script and how the
script should work?

And the last question. Is it a good idea for script to first look for .m12rc
in the current directory, then in ~/ and then in /etc?

I’m asking all these questions because I what to implement config files in my
small script and I want to make the correct decisions about the design.

Answer 1

The book ‘The Art of Unix Programming’ by E S Raymond discusses such issues.

You can override the config file with --config-file=/dev/null.

You would normally use the order:

• System-wide configuration (/etc/m12/m12rc, or just /etc/m12).
• User’s personal configuration (~/.m12rc)
• Local directory configuration (./.m12rc)
• Command-line options

with each later-listed item overriding earlier listed items. You should be able to specify the configuration file to read on the command line; arguably, that should be given precedence over other options. Think about --no-system-config or --no-user-config or --no-local-config. Many scripts do not warrant a system config file. Most scripts I’ve developed would not use both local config and user config. But that’s the way my mind works.

The way I package standard options is to have a script in $HOME/bin (say m12a) that does it for me:

#!/bin/sh
exec m12 --enable_feature --select=3 "$@"

If I want those options, I run m12a. If I want some other options, I run raw m12 with the requisite options. I have multiple hundreds of files in my personal bin directory (about 500 on my main machine, a Mac; some of those are executables, but many are scripts).