ADR-0015: POSIX escape processing inside bracket classes

• Status: Accepted
• Date: 2026-09-02

Context

zlob 1.6.3 does not process backslash escapes inside bracket classes. Bash, glibc fnmatch, BSD fnmatch, and Ferralk instead consume an enabled escape before interpreting class members and ranges. The difference affects escaped dashes, closing brackets, range endpoints, and whether the backslash itself is a member.

Decision

Ferralk keeps POSIX/Bash-style escape processing inside bracket classes. With escaping enabled, \\x contributes x to the class grammar and the backslash is not a member. The nine class-* divergences cite this ADR; zlob's result is retained only as differential evidence.

Consequences

• Character-class behavior agrees with the established shell and C-library references used by Ferralk.
• Compatibility with zlob's class parser is deliberately not promised.