CISS.debian.installer/lib/cdi_0005_guard/README.md

Table of Contents

• 1. CISS.debian.installer
• 2. Guarding and Safe Execution – cdi_0005_guard
• 2.1. Purpose and Functionality
• 2.2. Requirements
• 2.3. Dependencies
• 2.4. License
• 2.5. Author

1. CISS.debian.installer

Centurion Intelligence Consulting Agency Information Security Standard
The CISS Debian Installer provides a fully automated and hardened installation process.
Master Version: 8.00
Build: V8.00.000.2025.06.17

2. Guarding and Safe Execution – cdi_0005_guard

This directory provides minimalistic but critical utility functions to ensure safe and idempotent sourcing and execution semantics within the CISS.debian.installer framework. These wrappers act as foundational safeguards against redundant sourcing, which are frequent sources of bugs and side effects in modular Bash-based systems.

2.1. Purpose and Functionality

• 0005_guard_sourcing.sh
  Defines the guard_sourcing() function, which programmatically prevents a Bash library file from being sourced multiple times. It constructs a uniquely scoped read-only environment variable guard to mark the sourced state.

• 0006_source_guard.sh
  Implements the source_guard() function, which sources a given file only once. It uses the file’s basename to construct a similarly structured guard variable. Intended for cases where sourcing decisions must be made dynamically.

• 0011_guard_safe_exec.sh
  Provides a generic safe_exec() wrapper to execute external commands in a structured and error-controlled manner. It emits meaningful error logs using do_log() and allows associating custom error codes per invocation context. This is essential for defensive script execution when pipefail and strict traps are enabled.

2.2. Requirements

• Bash version ≥ 5.1
• Active error trapping via trap 'trap_err' ERR
• do_log() must be declared elsewhere in the global context
• All libraries must be sourced via source_guard() and invoke guard_sourcing on top

2.3. Dependencies

• Pure Bash implementation
• Uses declare -grx to enforce immutability and exportability of guard variables
• safe_exec() expects a predefined do_log() implementation

2.4. License

This component is dual-licensed under the European Union Public License v1.2 (EUPL-1.2), or the CoreSecret Custom Contributor License Agreement (CCLA-1.0). You may choose either license as per your usage context. Usage is permitted under the condition that no warranty is implied. Use at your own risk.

2.5. Author

Developed and maintained by
Marc S. Weidner
Centurion Intelligence Consulting Agency

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