CLI functionality is simple. It reads a config that specifies a list of files and nodes. The user can then apply or unapply patches.

Command Line Usage

env-applier-rs or (ea) is a CLI tool for applying environment variables in configuration files.

Basic Usage

ea [COMMAND] [OPTIONS]

Commands

apply

Applies the configuration by replacing variables in the target files with values from the environment.

ea apply [OPTIONS]

Options:
  -c, --config <FILE>  Path to config file
  -h, --help          Print help information

deapply

Reverts the configuration by restoring the original values in the target files.

ea deapply [OPTIONS]

Options:
  -c, --config <FILE>  Path to config file
  -h, --help          Print help information

parse

Validates the configuration file without making any changes to the target files.

ea parse [OPTIONS]

Options:
  -c, --config <FILE>  Path to config file
  -h, --help          Print help information

Global Options

-h, --help       Print help information
-V, --version    Print version information

Examples

Apply configuration using the default config file (config.toml):

ea apply

Apply configuration using a specific config file:

ea apply --config ./config.toml

Validate a specific config file:

ea parse --config ./some-config.toml

Revert changes using the default config file (config.toml):

ea deapply

Notes

• If no config file is specified, the tool will look for the default configuration file config.toml in your current working directory
• The tool will load environment variables from your system, .env & .env.local
• The parse command can be used to validate config files before applying changes

Configuration

The configuration file is what tells Env Applier what to change and where. It should be a single Toml file located in the current working directory or specified using the command argument for config.

By default config.toml is loaded by the CLI.

[environment]
# In this case the de-apply output would be something like "%%SOME_ENV_NAME%%"
prefix = "%%" # What env variables should be prefixed with when changes are de-applied
suffix = "%%" # What env variables should be suffixed with when changes are de-applied

[specific]
    [specific.json]
    [specific.toml]
    [specific.properties]
    [specific.yaml]
        [[specific.yaml.locations]]
        file = "test.yml" # The file which contains the config node
        node = "database.password" # The config node to change
        variable = "DB_PASS" # This is the env variable that is parsed on apply, and replaced back on de-apply

        [[specific.yaml.locations]]
        file = [ "test.yml", "test2.yml", ] # Allows multiple files to be updated
        node = "database.host" 
        variable = "DB_HOST"

        [[specific.yaml.locations]]
        file = "test.yml"
        node = [ "database.name", ] # Allow multiple nodes to be updated
        variable = "DB_NAME"

        [[specific.yaml.locations]]
        files = "test.yml" # Alias of "file"
        nodes = "server.password" # Alias of "node"
        variable = "DB_PASS"
        default = "%%OVERRIDE_DEAPPLY%%" # Overrides the "variable" field when de-applying
        override = { exemptApply = false, exemptDeapply = false } # Exempt from applying or de-applying changes

        [[specific.yaml.locations]]
        files = [ "test.yml", ] # Alias of "file"
        nodes = [ "database.password", "server.password" ] # Alias of "node"
        variable = "DB_PASS"
        default = "%%DB_CUSTOM_VARIABLE%%"
        override = { exemptApply = false, exemptDeapply = false }

Environment Variables

Environment variables are loaded from your system and the files .env & .env.local (Located in your current working directory).

.env files follow .properties format and support variable expnasion. Here is an example .env file which makes the following environment variables available to the program:

# SQL Database Settings
DB_NAME=database
DB_USER=root
DB_PASS=123
DB_HOST=localhost
DB_PORT=3306

# Example of variable expansion
DB_URL=mysql://$DB_USER:$DB_PASS@$DB_ADDRESS/$DB_NAME
DB_ADDRESS=$DB_HOST:$DB_PORT

File Formats

Format	Comments Support	Table Support	Array Support
YAML	✅ (Using #)	✅ (Maps)	✅ (Sequences)
JSON	❌	❌	✅
JSONC	✅ (Using //)	❌	✅
TOML	✅ (Using #)	✅	✅
Properties	✅ (Using #/!)	❌	❌

The specs & criteria for modifications is straightforward:

• Only replaces the value of a node, it never adds entries to the file
• Does not "reformat" the file at all
• Respects previous whitespace/indentation/line endings
• Respects comments in applicable config formats (Including header, footer & trailing comments)
• Able to traverse & modify complex data structures in supported file formats
• Editing a file should never break the syntax of the config