Rei User Guide

Rei is your calm study companion: keep todos, deadlines, and events in one place, find what matters, and take things one task at a time.

Get started

1. Install Java 25. In a terminal, run java -version to check your version.
2. Download rei.jar from the latest release.
3. Put the JAR in a folder where you can save files. Open a terminal in that folder and run java -jar rei.jar.
4. Type todo read book into the field at the bottom and press Enter or Send.

The window can be resized. Replies wrap to fit its width. Errors have a red outline and a Please try again heading; correct the command and send it again.

Commands at a glance

Use lowercase command names. Replace the CAPITALIZED placeholders below with your own values; do not type the placeholders themselves. Leading and trailing spaces, extra spaces between a command and its arguments, and tabs are accepted.

Action	Format	Example
Add a todo	todo DESCRIPTION	todo read chapter 6
Add a deadline	deadline DESCRIPTION /by DATE TIME	deadline submit report /by 2026-09-18 1800
Add an event	event DESCRIPTION /from DATE TIME /to DATE TIME	event study group /from 2026-09-18 1400 /to 2026-09-18 1600
Show tasks	list	list
Complete a task	mark NUMBER	mark 1
Reopen a task	unmark NUMBER	unmark 1
Remove a task	delete NUMBER	delete 1
Add a tag	tag NUMBER #TAG	tag 1 #school
Find by text	find TEXT	find report
Find by tag	find #TAG	find #school
Find by date	find DATE	find 2026-09-18
Exit	bye	bye

Add and manage tasks

Todos need a description. Deadlines also need a due date and time. Events need both a start and an end, with the end strictly later than the start. Include spaces around /by, /from, and /to, and supply each required separator once.

For example, todo read chapter 6 produces:

One less thing to remember. I've added: [T][ ] read chapter 6
You have a total of 1 tasks in the list.

In list, [T] is a todo, [D] a deadline, and [E] an event. [X] means done; [ ] means not done. Completed tasks stay in the list until you delete them. Repeated task descriptions are allowed, for example when the same reading is assigned twice.

Use the number shown by list or find for mark, unmark, delete, and tag. Numbers start at 1. Deleting a task renumbers later tasks, so check list again before your next change. Deletion has no undo; re-add the task if needed.

Dates and times

Dates accept yyyy-MM-dd, yyyy/MM/dd, dd/MM/yyyy, or dd-MM-yyyy. For day-first formats, one-digit days and months also work, such as 9/2/2028. Times use four-digit, 24-hour format: 0900 is 9 AM and 1800 is 6 PM. Use a space between date and time. Times are local clock times without time zones. Impossible dates and times, such as February 30 or 2400, are rejected.

find DATE shows deadlines due on that day and events overlapping that calendar day, including their start and end dates. It does not show undated todos. Date-shaped searches are treated as dates; other searches match description text.

Find and organize

find report matches descriptions containing report, ignoring letter case. A phrase such as find read book matches that contiguous phrase. Results retain their original list numbers, so you can act on a match directly.

Tags start with #, followed by letters A-Z, digits, underscores, or hyphens. Add one tag per command. tag 1 #School stores #school; adding it again is rejected. find #school matches that exact tag, ignoring case. A task can have multiple tags. There is no command for removing a tag.

Saving and recovery

Rei automatically saves each successful task change to data/rei.txt, relative to the folder from which you launch it. Keep that folder consistent between runs. A missing data file starts an empty list and is created on the first saved change. Back up data/rei.txt before moving or manually repairing it.

If saving fails, Rei reports the problem and leaves your tasks unchanged. Check that the folder is writable and that data/rei.txt is a file, then retry.

If the saved file cannot be read or contains damaged records, Rei warns you and allows viewing and searching any valid tasks it could load. Changes are blocked to protect the original file. Close Rei, back up the file, restore a known good copy or repair it, and restart. Keep only one instance of Rei open per data folder.

For an unknown command, missing argument, or invalid task number, follow the example in the error message. list and bye take no extra arguments.

Credits

Rei builds on the NUS CS2103 iP starter and the SE-EDU JavaFX tutorial. Its name is inspired by Rei of IVE. Week 6 enhancements and this guide were developed with OpenAI Codex assistance and checked against the project’s tests.