Consistent error handling + exit codes in wallet balance check script (fixes #7889)

[freeagent0x]

Adds scripts/check_balance.sh (consistent error handling + documented exit codes) + scripts/test_check_balance.sh (mocked HTTP tests). Fixes #7889. Wallet: 0x3030dc31a5349ddba9578ce46844a4cedc7fa02c (ETH/Base)

[github-actions]

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[FlintLeng]

PR Review: Consistent Error Handling + Exit Codes in Wallet Balance Script

Reviewed on: 2026-08-13

Summary

Fixes #7889. Adds a new scripts/check_balance.sh with documented exit codes and consistent error handling. Every failure path prints a distinct error to stderr and exits with a specific code.

Exit Code Scheme ✅

Documented exit codes are the right design for a CLI tool meant to be scripted:

Code	Meaning	Use Case
0	success	Balance fetched and printed
1	usage error	Missing/invalid wallet address
2	network error	DNS/connect/timeout
3	bad response	Non-200 HTTP, malformed JSON, missing field
4	wallet not found	HTTP 404 from RPC

Critical promise: "The script NEVER prints a balance it did not actually receive." This is the correct fail-closed design.

Error Handling ✅

Network layer: curl failures are caught via the temp-file pattern (curl writes HTTP code to $code_file, stderr to $err_file). Connection failures → exit 2.

Response layer: HTTP 404 → exit 4 (wallet not found). HTTP non-200/404 → exit 3. Malformed JSON (jq parse error) → exit 3. Missing amount_rtc field → exit 3.

Address validation: Basic regex ^[A-Za-z0-9]{20,64}$ rejects obvious garbage. Not cryptographic validation, but appropriate for a CLI sanity check.

Test Coverage ✅

test_check_balance.sh mocks the RPC with a Python HTTP server on a test port:

• goodwallet1234567890 → returns {"amount_rtc": "42.5"} → expects exit 0
• missingwallet12345678 → returns 404 → expects exit 4
• malformedwallet123456 → returns not json → expects exit 3
• emptyfieldwallet12345 → returns {"hello": "world"} (no amount_rtc) → expects exit 3

All paths tested. The mock server is cleaned up via trap.

Minor Notes

1. Address regex is permissive: The regex allows any 20-64 char alphanumeric string, not just RTC addresses starting with "RTC". This is fine for a sanity check, but users could pass a Solana/ETH address and get a network error (exit 2 or 3) instead of a usage error (exit 1). Consider adding a prefix check if stricter validation is desired.

2. set -euo pipefail is correct. The script fails fast on errors and undefined variables.

Wallet: RTC019e78d600fb3131c29d7ba80aba8fe644be426e

✅ LGTM — clean, well-documented CLI tool with consistent exit codes and comprehensive test coverage.