Library Implementer (Bash)

Create well-structured Bash library files with reusable functions

Library Implementer (Bash)

The Library Implementer skill provides context injection for creating well-structured Bash library files with reusable functions following shell best practices.

Overview

Property	Value
Skill ID	ct-library-implementer-bash
Tier	2 (Execution)
Protocol	implementation
Tags	implementation, bash, library

Capabilities

1. Function Libraries - Create lib/*.sh files with related functions
2. Utility Functions - Implement shared helper functions
3. Module Design - Organize functions into cohesive modules
4. Documentation - Document function signatures and usage

When to Use

The dispatch algorithm selects ct-library-implementer-bash for:

• Tasks with keywords: bash, library, shell, lib/
• Tasks labeled: bash-library
• Task type: bash-library

Directory Structure

lib/
├── exit-codes.sh       # Exit code constants
├── output-format.sh    # JSON/human output formatting
├── validation.sh       # Input validation functions
├── file-ops.sh         # Atomic file operations
├── logging.sh          # Audit trail logging
├── config.sh           # Configuration management
└── {new-module}.sh     # Your new library

Library Template

#!/usr/bin/env bash
# lib/{module-name}.sh - Brief description of module purpose
#
# Functions:
#   function_name()     - Brief description
#   another_function()  - Brief description

# Guard against multiple sourcing
[[ -n "${_MODULE_NAME_LOADED:-}" ]] && return 0
readonly _MODULE_NAME_LOADED=1

# Dependencies
# source "${LIB_DIR:-./lib}/dependency.sh"

# ==============================================================================
# CONSTANTS
# ==============================================================================

readonly MODULE_CONSTANT="value"

# ==============================================================================
# FUNCTIONS
# ==============================================================================

# Brief description of what this function does
#
# Arguments:
#   $1 - arg_name: Description
#   $2 - arg_name: Description (optional, default: value)
#
# Returns:
#   0 on success, non-zero on failure
#
# Output:
#   Writes result to stdout
#
# Example:
#   result=$(function_name "arg1" "arg2")
#
function_name() {
  local arg1="$1"
  local arg2="${2:-default}"

  # Implementation
}

Naming Conventions

# Public functions: lowercase_with_underscores
get_task_by_id()
validate_json_schema()

# Private/internal functions: prefix with underscore
_internal_helper()
_parse_config()

# Module-specific prefix for clarity
rm_get_entry()        # research-manifest module
orc_build_prompt()    # orchestrator module

Input Validation

function_name() {
  local required_arg="$1"
  local optional_arg="${2:-default}"

  # Validate required arguments
  if [[ -z "$required_arg" ]]; then
    echo "ERROR: required_arg is required" >&2
    return 1
  fi

  # Implementation
}

Error Handling

function_name() {
  local file="$1"

  # Check preconditions
  if [[ ! -f "$file" ]]; then
    echo "ERROR: File not found: $file" >&2
    return "${EXIT_FILE_ERROR:-4}"
  fi

  # Safe operation
  local result
  if ! result=$(risky_operation 2>&1); then
    echo "ERROR: Operation failed: $result" >&2
    return 1
  fi

  echo "$result"
}

JSON Output

get_data() {
  local id="$1"
  local format="${2:-json}"

  local data
  data=$(fetch_data "$id")

  if [[ "$format" == "json" ]]; then
    jq -nc --arg id "$id" --arg data "$data" \
      '{"id": $id, "data": $data}'
  else
    echo "ID: $id"
    echo "Data: $data"
  fi
}

Module Organization

Single Responsibility

# GOOD: lib/research-manifest.sh
# - All functions related to research manifest operations

# BAD: lib/utils.sh
# - Grab bag of unrelated functions

Dependency Layers

Layer 0: exit-codes.sh (no deps)
Layer 1: output-format.sh (deps: exit-codes)
Layer 2: validation.sh (deps: exit-codes, output-format)
Layer 3: Your module (deps: layers 0-2)

Execution Flow

1. Read task details
2. Set focus
3. Create library file in lib/
4. Verify syntax: bash -n lib/{module}.sh
5. Append manifest
6. Complete task
7. Return summary

Output Location

Libraries are created in: lib/{{MODULE_NAME}}.sh

Related Skills

• Test Writer - Creates tests for libraries
• Task Executor - General implementation
• Validator - Validates code quality