modify-jekyll-config-yml.rb

# script.rb
require 'yaml'

# Load the existing configuration
config = YAML.load_file('_config.yml')

# Modify the configuration using ENV variables
config['some_setting'] = ENV['MY_ENV_VARIABLE'] || 'default_value'

# Write the modified configuration to a new file
File.open('_config_temp.yml', 'w') { |f| f.write(config.to_yaml) }

# Now use this config file to build the Jekyll site
system("jekyll build --config _config_temp.yml")