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https://github.com/nbari/cron-parser

cron parser
https://github.com/nbari/cron-parser

cron cron-expression cron-format cron-parser crontab crontab-expressions parser

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cron parser

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# cron parser

[![crates.io](https://img.shields.io/crates/v/cron-parser.svg)](https://crates.io/crates/cron-parser)
[![Test](https://github.com/nbari/cron-parser/actions/workflows/test.yml/badge.svg)](https://github.com/nbari/cron-parser/actions/workflows/test.yml)
[![docs](https://docs.rs/cron-parser/badge.svg)](https://docs.rs/cron-parser)

Library for parsing cron expressions with timezone support.

Example:

use chrono::{TimeZone, Utc};
use chrono_tz::Europe::Lisbon;
use cron_parser::parse;

fn main() {
if let Ok(next) = parse("*/5 * * * *", &Utc::now()) {
println!("when: {}", next);
}

// passing a custom timestamp
if let Ok(next) = parse("0 0 29 2 *", &Utc.timestamp(1893456000, 0)) {
println!("next leap year: {}", next);
assert_eq!(next.timestamp(), 1961625600);
}

assert!(parse("2-3,9,*/15,1-8,11,9,4,5 * * * *", &Utc::now()).is_ok());
assert!(parse("* * * * */Fri", &Utc::now()).is_err());

// use custom timezone
assert!(parse("*/5 * * * *", &Utc::now().with_timezone(&Lisbon)).is_ok());
}

Cron table:

```
# ┌───────────────────── minute (0 - 59)
# │ ┌─────────────────── hour (0 - 23)
# │ │ ┌───────────────── dom (1 - 31) day of month
# │ │ │ ┌─────────────── month (1 - 12)
# │ │ │ │ ┌───────────── dow (0 - 6 or Sun - Sat) day of week (Sunday to Saturday)
# │ │ │ │ │
# │ │ │ │ │
# │ │ │ │ │
# * * * * *
```

| Field | Required | Allowed values | Allowed special characters |
| ------------ | -------- | -------------- | -------------------------- |
| Minutes | Yes | 0–59 | \* , - / |
| Hours | Yes | 0–23 | \* , - / |
| Day of month | Yes | 1–31 | \* , - / |
| Month | Yes | 1–12 | \* , - / |
| Day of week | Yes | 0–6 or Sun-Sat | \* , - / |

> For the day of the week, when using a Weekday (Sun-Sat) the expression `*/Day` is not supported instead
> use the integer, reasons for this is that for example `*/Wed` = `*/3` translates
> to run every 3rd day of week, this means Sunday, Wednesday, Saturday.

* `*` any value
* `,` value list separator
* `-` range of values
* `/` step values

Depends on crate [chrono](https://crates.io/crates/chrono).

Example of `Cargo.toml`:

[dependencies]
chrono = "^0.4"
cron-parser = "*"

Getting the next 10 leap year iterations:

use chrono::{DateTime, Utc};
use cron_parser::parse;

fn main() {
let now = Utc::now();
let mut crons = Vec::>::new();
let mut next = parse("0 0 29 2 *", &now).unwrap();
for _ in 0..10 {
next = parse("0 0 29 2 *", &next).unwrap();
crons.push(next);
}
for x in crons {
println!("{} - {}", x, x.timestamp());
}
}

It will print something like:

2024-02-29 00:00:00 UTC - 1709164800
2028-02-29 00:00:00 UTC - 1835395200
2032-02-29 00:00:00 UTC - 1961625600
2036-02-29 00:00:00 UTC - 2087856000
2040-02-29 00:00:00 UTC - 2214086400
2044-02-29 00:00:00 UTC - 2340316800
2048-02-29 00:00:00 UTC - 2466547200
2052-02-29 00:00:00 UTC - 2592777600
2056-02-29 00:00:00 UTC - 2719008000
2060-02-29 00:00:00 UTC - 2845238400