Bash Generation Engine
Bash Generation Engine
The core of the Statusline Editor is a deterministic generation engine that translates your visual configuration into a portable, high-performance Bash script. This engine ensures that the complex logic required for real-time status updates is encapsulated in a single file compatible with the Claude Code statusline setting.
How the Script Works
The generated script acts as a transformer. Every time Claude Code prepares a prompt, it sends a JSON payload to the script's stdin. The engine generates a script that follows a three-stage lifecycle:
- Ingestion: Reads the JSON input and extracts environment variables using
jq. - Processing: Performs calculations (like context percentage or token formatting) and fetches external data (like usage limits) if required.
- Rendering: Outputs a single line of text formatted with ANSI escape codes for the terminal.
Data Extraction & Processing
The engine maps specific UI blocks to key paths within the Claude Code JSON schema:
| Block | Source Data (JSON Path) | Processing Logic |
| :--- | :--- | :--- |
| Model | .model.display_name | Strips the "Claude " prefix for brevity. |
| Context % | .context_window.used_percentage | Rounds to the nearest integer. |
| Tokens | .total_input_tokens, .total_output_tokens | Formats large numbers (e.g., 12400 → 12.4k). |
| Directory | .cwd or .workspace.current_dir | Detects current working directory. |
Advanced Usage Tracking
One of the engine's most sophisticated features is the Usage Limits (OAuth) integration. If you enable "Rate 5h" or "Rate Week" blocks, the engine injects a robust sub-routine into the script that:
- Identifies the OS: Uses
uname -sto determine how to retrieve credentials. - Secure Credential Retrieval: Pulls the Claude Code OAuth token from the system's native secure storage (macOS Keychain, Linux
libsecret, or Windows Credential Manager). - Smart Caching: To prevent the statusline from lagging your terminal, the engine implements a local cache (
~/.claude/.usage-cache.json) with a 2-minute TTL. - Time Calculations: Since Bash is limited in date-time arithmetic, the engine embeds a Python 3 snippet to calculate the exact time remaining until your rate limits reset.
Visual Formatting System
The engine translates UI styles into low-level terminal commands:
ANSI Color Mapping
Colors selected in the editor are converted from ANSI 256-color codes to shell escape sequences. For example, selecting "Green (82)" results in:
\033[38;5;82m
Progress Bar Logic
Visual bars (Classic, Diamond, Dot, etc.) are generated using a math-based rendering loop. The engine calculates the number of "filled" vs. "empty" characters based on the percentage values provided by Claude Code.
# Example of generated bar logic
filled=$((percent * length / 100))
empty=$((length - filled))
# Outputs: ▓▓▓▓░░░░
Dependency Management
The engine is designed for minimal footprint but requires a few standard tools to handle complex data:
jq: Used for all JSON parsing.python3: Used for timezone-aware time calculations and OAuth token extraction from nested JSON.curl: Used to query the Anthropic API for usage data.
Example Output Structure
The final script follows a structured template:
#!/bin/bash
# 1. Capture JSON from Claude Code
JSON_INPUT=$(cat)
# 2. Extract core variables
model=$(echo "$JSON_INPUT" | jq -r '.model.display_name')
percent=$(echo "$JSON_INPUT" | jq -r '.context_window.used_percentage')
# 3. Conditional logic (Usage Limits)
# [Fetch usage from API or Cache...]
# 4. Final Render
echo -e "\033[38;5;254m[$model]\033[0m | \033[38;5;82m${percent}%\033[0m"