bash-script-generator

name	bash-script-generator
type	standard
depth	extended
description	Generates production-ready bash 5.2+/5.3 scripts with strict mode, immutable locals, dispatch tables, and functional patterns. Use when creating new .sh scripts, CLI tools, cron jobs, deployment automation, text processing workflows, or log analyzers.

[H1][BASH-SCRIPT-GENERATOR]

Dictum: Functional patterns and strict mode produce maintainable shell automation.

Generate bash scripts with immutable locals, dispatch tables, pure functions, and zero mutable state.

Tasks:

1. Clarify requirements — Purpose, I/O, shell type, args, error strategy, performance constraints.
2. Read bash-scripting-guide.md — Strict mode, parameter expansion, arrays, bash 5.2/5.3 features.
3. Read script-patterns.md — Argument parsing, logging, parallel processing, retry, signals.
4. Read text-processing-guide.md — rg/awk/sd selection, pipeline patterns, performance.
5. Structure script — Shebang + strict mode + readonly constants + trap + main.
6. Implement — Core functions, business logic, main entry point.
7. Validate — bash -n script.sh, ShellCheck 0.11.0+, re-validate until clean.

---

[1][REQUIREMENTS]

Dictum: Ambiguity resolution prevents rework.

Clarify before generating:

[INDEX]	[AMBIGUITY]	[QUESTION]
[1]	Data format	Input format? (nginx combined, JSON, CSV, custom)
[2]	Large files	Files >100MB? Optimize for memory/performance?
[3]	Error handling	Fail fast, continue with warnings, or retry?
[4]	Portability	POSIX sh portability or bash 5.2+/5.3?
[5]	Output format	Human-readable, JSON, or CSV?

Guidance:

• Architecture First: Explain design, tool selection rationale, key tradeoffs before writing code.
• Data Format Routing: JSON? jq. YAML? yq eval. CSV/TSV? miller (mlr). Interactive exploration? jnv.
• Template: Reference assets/templates/standard-template.sh for production boilerplate.

---

[2][STRICT_MODE]

Dictum: Strict mode prevents silent failures.

#!/usr/bin/env bash
set -Eeuo pipefail          # -E = errtrace (ERR trap inherits into functions/subshells)
shopt -s inherit_errexit    # Command substitutions inherit errexit
IFS=$'\n\t'

Guidance:

• Scope: Every generated script includes this block. No exceptions.
• Disable: Temporarily suppress — output=$(cmd 2>&1) || handle_error "${output}".

---

[3][FUNCTIONAL_STYLE]

Dictum: Immutability and dispatch tables eliminate mutable state.

[INDEX]	[RULE]	[PATTERN]
[1]	Immutable locals	local -r for all non-mutating variables inside functions
[2]	Immutable globals	readonly for all module-level constants
[3]	Pure functions	Input via args, output via stdout or nameref (local -n), no global state
[4]	Dispatch tables	declare -Ar for O(1) routing; case/esac only for pattern matching
[5]	Higher-order	Pass function names as args; local -n nameref for array parameters
[6]	Inline trivials	Single-use < 3 lines: inline at call site
[7]	Brace grouping	{ cmd1; cmd2; } > file over ( ... ) (no subshell)
[8]	No mutable counters	${#arr[@]}, rg -c, or awk pipelines for counting
[9]	mapfile/readarray	Over while read loops for array population (3-5x faster)
[10]	printf everywhere	Over echo (handles escapes, format strings, no ambiguity)
[11]	$(<file)	Over $(cat file) (no fork)
[12]	printf -v	printf -v var '%(%F %T)T' -1 over $(date ...) (no subshell)
[13]	Here-strings	<<< over echo x | cmd pipelines
[14]	BASH_REMATCH	+ over /

Best-Practices:

• Nameref Constraint: Array variables cannot be namerefs, but namerefs can reference arrays.
• Dispatch Declaration: declare -Ar assigns on declaration line; separate assignment fails for readonly.
• Structured Checks: declare -Ar CHECKS=([name]="pattern\|msg\|level") + IFS=\| read -r for data-driven validation.

---

[4][QUALITY_GATE]

Dictum: Checklists prevent omissions.

[VERIFY] Generation:

• #!/usr/bin/env bash + set -Eeuo pipefail + shopt -s inherit_errexit + IFS=$'\n\t'.
• All variables quoted: "${var}".
• Constants: readonly UPPER_SNAKE; locals: local -r; functions: lower_snake().
• printf -v var '%(%F %T)T' -1 for timestamps (no $(date) subshell).
• [[ ]] over [ ]; <<< over echo |; <() over temp files.
• Cleanup: trap cleanup EXIT (single trap, EXIT covers normal + signal exits).
• ShellCheck 0.11.0+ clean; no eval with user input; $() over backticks.
• Usage/help with examples; post-generation summary with tool selection rationale.

[REFERENCE]: docs/bash-scripting-guide.md — Language features, parameter expansion, arrays. [REFERENCE]: docs/script-patterns.md — Argument parsing, logging, parallel, retry. [REFERENCE]: docs/text-processing-guide.md — Tool selection, rg/awk/sd, performance.