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Core Function Library

This chapter explains the core function library of bash-cli, which provides reusable functions for common tasks, promoting consistency and reducing code duplication. Imagine you are building a CLI and need consistent output formatting and a robust way to handle command dispatching. The core function library addresses these needs.

Introduction

The core function library of the bash-cli framework resides in the bash-cli.inc.sh file. This file contains a collection of Bash functions that are used throughout the framework for various purposes, including:

  • Path Resolution: Handles absolute path resolution.
  • String Manipulation: Provides utilities for tasks like trimming whitespace.
  • Output Formatting: Defines color constants and functions for displaying formatted output.
  • Core CLI Logic: Implements the command dispatching mechanism, help generation, and Bash completions.

Using the Core Functions

This section demonstrates how to use some of the key functions provided by the library.

Path Resolution

The bcli_resolve_path function resolves a given path to its absolute form.

source bash-cli.inc.sh

path=$(bcli_resolve_path "./relative/path")
echo "$path" # Output: /absolute/path/to/relative/path (example)

This function ensures that you are working with absolute paths, regardless of the user's current working directory. It uses realpath if available, and falls back to a Perl solution for compatibility with systems like macOS.

String Manipulation

The bcli_trim_whitespace function removes leading and trailing whitespace from a string.

source bash-cli.inc.sh

string="  string with whitespace  "
trimmed_string=$(bcli_trim_whitespace "$string")
echo "$trimmed_string" # Output: string with whitespace
This is useful for cleaning user input or formatting output.

Output Formatting

The library defines color constants and provides functions for styled output.

source bash-cli.inc.sh

echo -e "${COLOR_RED}This is red text${COLOR_NORMAL}" # Output: This is red text (in red color)

The bcli_show_header function displays a formatted header for your CLI application.

source bash-cli.inc.sh

bcli_show_header "<project_root>/app" # Output: CLI Name, Version, and Author from .name, .version, and .author files.

This function reads the .name, .version, and .author files from your application directory and displays them in a formatted header.

Internal Implementation

The bash-cli.inc.sh file is sourced by both the main cli script and the complete script. This allows both scripts to access and utilize the shared functions. The cli script uses the bcli_entrypoint function for command dispatching, while the complete script uses bcli_bash_completions for Bash completions.

The following sequence diagram illustrates the interaction between the cli script and the core functions for command dispatching:

sequenceDiagram
    participant CLI
    participant bcli_entrypoint
    participant bcli_resolve_path
    participant Command Script

    CLI->>bcli_entrypoint: Execute command
    bcli_entrypoint->>bcli_resolve_path: Resolve path
    bcli_entrypoint->>Command Script: Execute command script
    Command Script-->>bcli_entrypoint: Return exit code
    bcli_entrypoint-->>CLI: Return exit code

Command Dispatching (bcli_entrypoint)

The bcli_entrypoint function in bash-cli.inc.sh (explained in Command Dispatcher) handles the logic for locating and executing the appropriate command script based on user input. It uses bcli_resolve_path to resolve paths, and if the command requires help, it leverages the bcli_help function (explained in Help Generation ).

Bash Completions (bcli_bash_completions)

The bcli_bash_completions function in bash-cli.inc.sh (explained in Bash Completion Logic ) provides Bash completion functionality for your CLI. It dynamically generates completion suggestions based on available commands and options.

Conclusion

The core function library is essential to the bash-cli framework, providing reusable functionality for common tasks and ensuring consistency across your CLI application. By leveraging these functions, you can simplify your CLI development process and create a more robust and user-friendly command-line interface.

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