Subversion Repositories perlutils

# perlConfigFileUtility

A Perl utility for managing configuration files with template merging, interactive editing, and format conversion capabilities.

## Overview

`perlConfigFileUtility` is designed to simplify configuration file management by:

- Merging template structures with existing configuration files

- Providing an interactive hierarchical editor for modifying configurations

- Converting between YAML and JSON formats

- Automatically backing up config files when saving changes

## Background

This utility solves two primary problems:

1. **User-Friendly Editing**: Enables users unfamiliar with JSON/YAML syntax to safely edit configuration files through an interactive interface.

2. **Version Compatibility**: Handles configuration file evolution across software versions. When new key/value pairs are added to the application, the utility merges them with existing config files, ensuring older configurations remain compatible with newer software.

### Implementation Approach

- Default configuration is stored as a Perl data structure in a separate file (loaded via `do` statement in project script)

- This template can be shared across multiple applications

- The utility loads existing YAML/JSON configs, merges missing values from the template, and presents an interactive editor

- Format conversion (YAML ↔ JSON) was added as a natural extension of the merge functionality

## Features

- **Template Merging**: Combine Perl data structure templates with existing YAML/JSON config files

- **Interactive Editor**: Navigate and edit nested hashes and arrays with a menu-driven interface

- **Dynamic Modifications**: Add new keys to hashes and elements to arrays on the fly

- **Delete Operations**: Remove keys from hashes and elements from arrays, including all nested children

- **Format Conversion**: Seamlessly convert between YAML and JSON configuration formats

- **Safe Updates**: Automatic backup creation before saving changes

## Usage

```bash

# Basic usage

perlConfigFileUtility [-t <template_file>] [-c <config_file>] [-o <output_file>] [-e]

# Positional arguments (backward compatibility)

perlConfigFileUtility <template_file> [config_file]

```

## Example of template file

The template file is a Perl hash reference that defines the complete configuration structure with default values and inline documentation. Below is a simplified excerpt from the `sneakernet` project's datastructure file (see `../zfs_utils/sneakernet/sneakernet.datastructure` for the full example).

```perl

# Default configuration structure for sneakernet

# This file is loaded by the sneakernet script to provide default configuration values

# Variables from $programDefinition hashref (scriptDirectory, scriptFullPath) will be interpolated at runtime

{

   'dryrun' => 0, # if set to 1, will not perform any changes, just log what would be done

   'verbosity' => 1, # verbosity level for logging

   'debug' => 0, # set to number greater than 0 for debugging program

   'status_file' => "<scriptDirectory>/sneakernet_target.status", # file created on source server to track last copied dataset

   'log_file' => "<scriptFullPath>.log",

   'displayLogsOnTTY' => '', # if set to path of a tty, log messages will be sent there also. Example: /dev/ttyv1

   'displayLogsOnConsole' => 1, # If set to non-zero, will send log messages to screen in addition to log file

   'source' => { # information about source server

      'hostname' => '', # used to see if we are on source

      'poolname' => 'pool', # name of the ZFS default parent pool to export

      'cleanUpScriptsDir' => '<scriptDirectory>/cleanupScripts', # location on disk where scripts to be sent to target are located

      'report' => { # if set, will generate a report via email or by storing on a drive

         'email' => '', # if set, will email the report to this address

         'subject' => '', # subject of the report email (will be auto-generated if empty)

         'targetDrive' => { # if set, will store the report on this drive

            'label' => '', # the GPT or msdos label of the report drive, REQUIRED

            'fstype' => '', # filesystem type of the report drive, default is msdos

            'check_interval' => 15, # how often to check for the disk (seconds), message displayed every interval

            'wait_timeout' => 300, # time to wait for the disk to appear in seconds

            'mount_point' => '', # where to mount the report drive, default is /mnt/label

         }

      }

   },

   # ... additional sections: 'target', 'transport', 'datasets' (see full file)

}

```

### How it works

The template file serves dual purposes:

1. **Default Values**: The Perl script loads it at runtime using `$config = do 'scriptname.datastructure'`, which returns the hash reference with all defaults.

2. **Configuration Schema**: The inline comments document each setting's purpose, forming a self-documenting configuration schema that can be exported to YAML format (e.g., `scriptname.conf.yaml`).

When the datastructure changes, this tool can non-destructively merge the updated template with existing configuration files, preserving user customizations while adding new keys and documentation. The interactive edit mode (`-e`) provides safe, menu-driven configuration management.

## Options

| Option | Description |

|--------|-------------|

| `-t, --template <file>` | Template file (Perl hashref) |

| `-c, --config <file>` | Config file (YAML or JSON) |

| `-o, --output <file>` | Output file (default: STDOUT) |

| `-e, --edit` | Interactive edit mode |

| `-v, --version` | Show version information |

| `-h, --help` | Show help message |

## Requirements

- **Perl** 5.x or higher

- **File::Slurp** - File reading utilities

- **Data::Dumper** - Data structure serialization

- **Getopt::Long** - Command-line option parsing

## License

Simplified BSD License (FreeBSD License)  

Copyright (c) 2026, Daily Data Inc.

## Author

R. W. Rodolico <rodo@dailydata.net>

## Version

1.1.0 (January 2026)

### Version History

- **1.1.0** (2026-01-15): Added ability to delete keys from hashes and elements from arrays

- **1.0** (2026-01-13): Initial release with merge, edit, and format conversion capabilities