Safe parsing
Validates five required fields plus lists, ranges, steps and supported month or weekday names with clear errors.
100 Days of Code / Python / Local Automation
Cron Explainer
/ Overview
A dependency-free Python CLI that validates five-field cron expressions, explains each field and previews deterministic future matches.
Compact cron expressions are easy to misread, especially when lists, ranges, steps and the day-of-month or day-of-week rule appear together.
/ Provided servicesClear thinking.
Clear thinking.
Practical delivery.
Schedule explanation
Turns compact cron tokens into a scannable explanation while documenting common day matching semantics.
Deterministic preview
Calculates bounded future matches from a supplied ISO date and returns readable or structured output.
/ Solution
I built a dependency-free Python CLI that parses standard five-field expressions, validates bounded values, expands common syntax, explains every field and previews future matches from an optional fixed starting time. It never installs or executes a scheduled job.
/ Impact
Five-field cron validation
Readable field-by-field explanations
Deterministic future-match previews
Text and JSON reports
No job execution or system changes
Python standard library
Argument parsing, immutable data structures, date-time iteration and JSON output without external packages.
Cron semantics
Supports standard five-field local wall-clock schedules and the common OR rule for restricted month-day and weekday fields.
Unit tests
Nine deterministic tests cover invalid input, names, ranges, steps, Sunday normalization, match previews and bounded counts.