EdwinRy / cron_parser

Cron Expression Parser

The Cron Expression Parser is a command line utility which takes in a single line of a cron job expression and prints out a table of values describing at what times the cron job would run.

Quick Start

In order to use this program, you have to either compile it and run the executable, or use the go run command.
There is a Makefile provided to compile the program into a single executable called cronParser in the root of this project. If you have access to make and the go-lang 1.21 compiler in path you can run the following command from the root of this project to compile the program.

make

In order to run the program with sample input:

./cronParser "*/15 0 1,15 * 1-5 /usr/bin/find"

Using go without make

If make is unavailable on your system but you have a valid go 1.21 installation on your system and in path you can either compile it manually using commands found in the Makefile or you can run the following command from the root of project

go run cronParser "*/15 0 1,15 * 1-5 /usr/bin/find"

If you do not have go installed on your system, check out installing dependencies

Releases

There are a few pre-made releases found in the releases folder, these have been testes on darwin/amd64, darwin/arm64, and linux/amd64, it is not guaranteed they they will work on other systems.

Usage

The command is to be ran in the following format:

./cronParser "<cron string>"

The output of the command will look as follows:

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

Installing Dependencies

Go 1.21

As of January 2024, go1.21.6 is the latest stable release of go, you can download it for your system from the official go-lang website

go installation instructions are available here

If you are on MacOS and/or have homebrew installed you can install go using

brew install go@1.21

In case you have a different version of go installed on your system you can either replace it with go 1.21 or follow the official guide for managing multiple go installs here

Docs

The documentation.mkd file at the root of this project outlines the decision making and designs behind this project. It is recommended you use a markdown viewer (vscode works really well for that) for a better reading experience.