CSC 397 Lab Assignment 3

Assigned 24 September 1998

Due 1 October 1998

100 points, 5% of your course grade.

(Lab 1 is worth 8%, Lab 2 is worth 3%)

Cron is a Unix system daemon to execute commands at specific times. The command and time specifications are stored in files commonly known as crontabs. Cron wakes up once per minute to scan the crontabs, and execute any commands whose time specification matches the current time. There is a system crontab accessible only to the root user, and individual crontabs owned by various ordinary users and accessible only by the owner and root.

You will design a graphical user interface for the cron facility. This is to be a paper design only (you may prototype using Visual Basic if you wish, but it limits your imagination). Draw each screen on a separate sheet. They can be hand drawn but must be very neat (printed letters, straight lines drawn with ruler, proportional). Use as many sheets as necessary to illustrate all functions (one screen can implement multiple functions). The sheets should be accompanied by any written explanations (on separate pages; each screen should be numbered for reference).

Use your imagination! Determine some usability criteria, document those, then design with them in mind. Turn them in with your design. I will force this one on you: opportunities for user input error should be minimized.

REQUIRED FUNCTIONALITY:

• Gain access to this facility (your ID will determine which (if any) items and services you have access to).
• If user is root, select which crontab to work with. Should be able to switch within a session.
• Select a crontab item.
• Add a new command to crontab list (command and time/periodicity). The time fields are: minute, hour, day of the month, month of the year, day of the week. The value may either be a specific value or a wildcard (will always match when cron checks it). The wildcard is used for periodicity and is represented in the Unix CUI (command UI) as an asterisk (*).
• Remove an item from crontab list.
• Edit an item that is on the crontab list.
• Merge an existing crontab-formatted file into the current crontab.
• Display the current crontab.
• Save the current crontab.
• Display any cron-initiated commands currently running (root only).
• Select then terminate any cron-initiated command that is currently running (root only).
• Display all commands scheduled to run at specified time or time period (root only).
• Display all commands scheduled to run within X minutes or hours of current time (root only).
• Select method for determining who can have crontabs (root only). Choices are:

1. Only root.
2. All users.
3. Root plus only those users in an "allow" list.
4. Root plus all users except those in a "deny" list.

• Display allow/deny list (root only).
• Add or remove a user from allow/deny list if applicable (root only).
• Seek help information on any permissible functions.
• Exit from the application.