Parameter Expansion Patterns

Parameter expansion patterns I’ve actually used. Every entry has a date and context.

2026-04-04: Guard Missing Source Files

Problem: .zshenv sources ~/.cargo/env but file doesn’t exist until Rust is installed, causing warnings on every shell start

Context: P16g first boot, zsh startup errors

The Fix:

# WRONG: fails if file doesn't exist
source ~/.cargo/env

# RIGHT: guard with file existence check
[[ -f ~/.cargo/env ]] && source ~/.cargo/env

Rule: Always guard source commands with [[ -f path ]] — the file may not exist on every machine.

Worklog: WRKLOG-2026-04-04