Description

Cron expression parser loosely based on the format specified here: https://www.ibm.com/docs/en/db2/12.1?topic=task-unix-cron-format and here: https://en.wikipedia.org/wiki/Cron#:~:text=web%20hosting%20environment.-,Cron%20expression,-%5Bedit%5D

Allows for slash operators like "1/2" to be processed as "1-{last valid value}/2"

Features

• Parses standard UNIX-like cron expressions (minute, hour, day of month, month, day of week).

• Supports special characters ("*", "-", ",", "/").

• Outputs all valid values for each of the fields as per the given expression.

• All field names and their allowed values:

  Field name	Allowed values	Allowed special characters
  minute	0-59	* , / -
  hour	0-23	* , / -
  day of month	1-31	* , / -
  month	1-12	* , / -
  day of week	0-6	* , / -

Dependencies:

• Java 21 or above - https://www.oracle.com/java/technologies/downloads/#java21
• Maven - https://maven.apache.org/download.cgi
• Docker (optional) - https://docs.docker.com/get-started/get-docker/

Build

From project root, run:

$ mvn clean package

Test

From project root, run:

$ mvn verify

Current code coverage report:

Package	Missed Instructions	Coverage	Missed Branches	Branch Coverage	Complexity Missed	Complexity Covered	Missed Lines	Covered Lines	Missed Methods	Covered Methods	Missed Classes
org.cronparser.model	111	49%	10	50%	20	30	11	40	10	20	4
org.cronparser	15	0%	N/A	N/A	2	2	4	4	2	2	1
org.cronparser.parser.field	0	100%	1	97%	1	31	0	70	0	12	1
org.cronparser.parser	0	100%	0	100%	0	7	0	20	0	3	1

Total Coverage Summary

• Instructions: 82%
• Branches: 83%

Run

• Download jar from releases here - https://github.com/SantanuKar43/cron-parser/releases/tag/v1.0 and run:

$ java -jar cronparser-1.0-SNAPSHOT.jar "*/15 0 1,15 * 1-5 /usr/bin/find"

• If building from the source code, navigate to the project root directory and run:

$ mvn clean package
$ java -jar target/cronparser-1.0-SNAPSHOT.jar "*/15 0 1,15 * 1-5 /usr/bin/find"

• If using Docker, execute the run.sh script from the project root:

$ sh run.sh [expression]

Sample input-output

input:

$ sh run.sh "*/15 0 1,15 * 1-5 /usr/bin/find"

output:

minute        0 15 30 45
hour          0
day of month  1 15
month         1 2 3 4 5 6 7 8 9 10 11 12
day of week   1 2 3 4 5
command       /usr/bin/find