Cron Expression Parser

This Go program parses a cron expression and expands its fields into individual values. It also extracts and displays the command associated with the cron expression.

Features

• Parses standard cron expressions
• Expands fields for minutes, hours, day of the month, month, and day of the week
• Displays the parsed command

Usage

The program expects a cron expression as a single command line argument.

Example

Given the cron expression */15 0 1,15 * 1-5 /usr/bin/find, the program will produce the following 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

Requirements

• Go 1.16 or later

Setup

1. Install Go:

   Make sure you have Go installed on your machine. You can download it from https://golang.org/dl/.

2. Build the Project:

   Build the Go program using the following command:

   go build -o cron-parser cron_parser.go

3. Run the Program:

   Execute the compiled program with a cron expression as an argument:

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

Project Structure

cron-parser/
├── cron_parser.go
└── README.md

Code Overview

cron_parser.go

This file contains the main logic for parsing and expanding the cron expression. It includes the following functions:

• ParseCron: Parses the cron expression string into a Cron struct.
• expand: Expands a cron field into a list of values.
• printExpanded: Prints the expanded field values.
• main: The main entry point of the program that reads the command line argument, parses it, and displays the expanded fields.

Example Usage

To run the program, use the following command:

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

This will 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

Contributing

If you want to contribute to this project, please fork the repository and submit a pull request with your changes.

License

This project is licensed under the MIT License - see the LICENSE file for details.