tpt-cron-parse

Cron expression parser with precise error reporting and human-readable output. No dependencies.

Supports standard 5-field and extended 6-field (with seconds) cron syntax.

Features

• 5-field (min hour dom month dow) and 6-field (sec min hour dom month dow) cron
• Precise errors — CronError includes the byte position, which field failed, what was expected, and what was found
• Human-readable — to_human_readable() converts expressions to English
• No dependencies — pure Rust

Usage

use tpt_cron_parse::CronExpr;

let expr = CronExpr::parse("0 9 * * 1").unwrap();
println!("{}", expr.to_human_readable()); // Every Monday at 9:00 AM

let expr = CronExpr::parse("*/5 * * * *").unwrap();
println!("{}", expr.to_human_readable()); // Every 5 minutes

Error Reporting

use tpt_cron_parse::CronExpr;

let err = CronExpr::parse("x * * * *").unwrap_err();
println!("{}", err); // cron parse error in minutes field at position 0: expected digit, found 'x'

Human-Readable Examples

Computing the next run time

The crate stays dependency-free by default. Enable the optional chrono feature to compute the next firing time of a schedule:

[dependencies]
tpt-cron-parse = { version = "0.1", features = ["chrono"] }

use tpt_cron_parse::CronExpr;
use chrono::{TimeZone, Utc};

let expr = CronExpr::parse("0 9 * * 1-5").unwrap();
let after = Utc.with_ymd_and_hms(2024, 1, 1, 0, 0, 0).unwrap(); // Monday
let next = expr.next_after(after).unwrap(); // next weekday at 09:00

next_after respects the standard cron day-of-month / day-of-week OR rule and searches at most ~4 years ahead (the maximum period of a cron schedule).

License

Licensed under either of Apache License 2.0 or MIT at your option.