Cron Expression Parser

Overview

Parses Cron Expressions of the following format:

• (Minute) (hour) (day of month) (month) (day of week) (command)
• * means all possible time units
• - a range of time units
• , a comma separated list of individual time units
• / intervals time units, the left value is the starting value and the right value is the max value

For example given the input argument:

3,45/15 0 1,15 * 1-5 /usr/bin/find

The output should be:

minute        3 18 33 45 48
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

Running from gradle

./gradlew run --args="3,45/15 0 1,15 * 1-5 /usr/bin/find"

or

./gradlew run --args="-arguments 3,45/15 0 1,15 * 1-5 /usr/bin/find"

Running built jar

The build will build two jars:

1. A plain jar that is built for use a library at build/libs/cron-parser.jar
2. A shadow jar that is built for running as a standalone application build/libs/cron-parser-all.jar

To run the shadow jar if you are planning to pass any arguments with * notation you may need to configure your terminal to disable globbing. I found that using zsh shell on my mac this was and issue. If I try to run the following command:

java -jar build/libs/cron-expression-parser-java-{version}-all.jar 3,45/15 0 1,15 * 1-5 /usr/bin/find

or

java -jar build/libs/cron-expression-parser-java-{version}-all.jar -arguments 3,45/15 0 1,15 * 1-5 /usr/bin/find

Then the following output is returned:

notation parser not found for value gradlew.bat

As you can see the * has been expanded to include files/folders from the current directory where the command is being run. This can be fixed by running the following command to disable globbing:

set -o noglob

Once globbing has been disabled, when the jar command list above is run again the following output will be displayed:

minute        3 18 33 45 48
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

Useful Commands

// cleans build directories
// prints currentVersion
// formats code
// builds code
// runs tests
// checks for gradle issues
// checks dependency versions
./gradlew clean currentVersion dependencyUpdates lintGradle spotlessApply build

Commit History

The code in this project was originally written in this exercises repo it was extracted out into its this repo once it became reasonably large. The original commit history can be found there.

Using Published Versions

A new version of the parser is published on each successful pipeline run against the master branch. You can download the runnable jar using the following URL (with the latest version inserted)

https://repo1.maven.org/maven2/com/github/michaelruocco/cron-expression-parser-java/{version}/cron-expression-parser-java-{version}-all.jar

When the jar is downloaded you can run it using the following command:

java -jar cron-expression-parser-java-{version}-all.jar 3,45/15 0 1,15 * 1-5 /usr/bin/find

Don't forget to run set -o noglob as mentioned previously above to turn of globbing if using a fresh terminal!

The library jar can also be used in a maven or gradle project using the standard dependency definitions outlined

https://search.maven.org/artifact/com.github.michaelruocco/cron-expression-parser-java