Where parallels cross

Interesting bits of life

Automate boring configuration changes

Sometimes we do repetitive actions that seem not worth to automate. The problem is that sometimes these affect morale and become time-consuming: for instance for lack of attention the configuration change introduces regressions, which cause an extra deployments to fix errors.

Well I had some time to wonder if I could automate adding entries to our one of our configuration file in a consistent way. And as a side effect I improved my Bash scripting skills.

The configuration file I am speaking about whitelists applications. Our configuration file contains entries which represent applications. Each entry has an unique identifier. Anytime an application requests a service, it has to submit this identifier: the request is fulfilled only if the identifier is in the configuration file.

When we insert a new entry manually, we have to satisfy two constraints:

So our Bash script will do the following sequentially:

  1. ask required input
  2. generate an uuid
  3. check if the generated uuid already exists and generate a new one until it does not
  4. make the entry
  5. append entry to the files

So here is the script:

## Usage: the script will request the necessary inputs to create a new application entry and will alter the configuration files in the repository.

files="some-dir/resources-local/configurationFile.json some-dir/resources-DEV/configurationFile.json some-dir/resources-TST/configurationFile.json some-dir/resources-ACC/configurationFile.json some-dir/resources-PRD/configurationFile.json"
# ask for user input
read -p 'Application name: ' appname
read -p 'Type: ' type
read -p 'Contact name: ' contact_name
read -p 'Maintainers email address: ' email
read -p 'Aim of the application: ' description
echo Current vars: $appname $type $email $description

# generate a new lowercase uuid (it must not be already in the file)
lowercase_uuid=$(echo $uuid | tr '[:upper:]' '[:lower:]')
echo New uuid: $lowercase_uuid
# retry if uuid already exists
while true; do
    if grep "$lowercase_uuid" $prd_file > /dev/null
        lowercase_uuid=$(echo $uuid | tr '[:upper:]' '[:lower:]')
        echo 'new uuid found in file, created a new one: ' $lowercase_uuid
        echo uuid not found
# end of retry

# make a new configuration entry
  "contactName": "'$contact_name'",\n
  "contactEmail": "'$email'",\n
  "description": "'$description'",\n
  "id": "'$lowercase_uuid'",\n
  "name": "'$appname'",\n
  "type": [

echo $entry

for file in "${files_array[@]}"
    # remove blank lines at the end of the file
    sed -i '' -e :a -e '/^\n*$/{$d;N;};/\n$/ba' $file
    # remove last line (because it contains "]")
    sed -i '' -e '$ d' $file
    # remove blank lines at the end of the file
    sed -i '' -e :a -e '/^\n*$/{$d;N;};/\n$/ba' $file
    # remove last line (because it contains "}")
    sed -i '' -e '$ d' $file

    # append entry
    echo '},\n' $entry '\n]' >> $file

This kind of script is not perfect, because it works on assumptions like:

However, this script made a configuration change a thoughtless process on my side. The only automation left is to ask people needing an identifier to open a merge request to the repository by using this script.

Maybe this can inspire you to hack (better than this) some small and frequent&boring tasks you have to do.

Happy hacking!