📅 GUI Cron Job Scheduler

A simple graphical user interface (GUI) application built with Python's Tkinter library to easily schedule new cron jobs on a Linux or macOS system. This scheduler not only sets up standard cron entries but also includes optional retry logic for the command being scheduled.

✨ Features

• Interactive GUI: User-friendly interface built with Tkinter.
• Full Cron Schedule: Allows input for all five standard cron fields (Minute, Hour, Day of Month, Month, Day of Week).
• Command Input: Easily specify the Bash script or command to be executed.
• Retry Logic (Optional): Define a maximum number of retries and an interval between retries for the command if its initial execution fails.
• Crontab Integration: Automatically checks the current crontab and appends the new job using the crontab - command.
• Validation: Basic validation for input bounds and mandatory fields.
• User Email Save: All cron tasks and their outcomes are posted by the cron daemon to the user's email. Available through the mail command.
• Runnable Check: Verifies if the specified command file exists and has execution permissions (via an external runnable_check module).

🛠️ Prerequisites

• Python 3: The application is written in Python 3.
• Tkinter: Usually bundled with standard Python installations.
• Linux/macOS: The cron and crontab command must be available on your operating system.

🚀 Installation and Setup

1. Download or Clone This GitHub Repo

   Make sure to save check all files exist locally.

2. Run the Application:

   python3 main.py

💻 Usage

1. Bash Command to Run

Enter the full path to the executable script or command you wish to schedule.

2. Cron Recurrence

Fill in the standard five cron fields. Use numbers, ranges (e.g., 1-5), steps (e.g., */10), or the asterisk (*) for "any value".

Field	Range	Description	Default
Minute	0-59	Minute within the hour.	* (Every minute)
Hour	0-23	Hour of the day.	* (Every hour)
Day of Month	1-31	Day of the month.	* (Every day)
Month	1-12	Month of the year.	* (Every month)
Day of Week	0-7	Day of the week (0 and 7 are Sunday).	* (Every day)

3. Cron Retries (Optional)

These fields configure the retry mechanism. Set Max Tries to 0 to disable retries.

Field	Range	Description	Default
Interval	0-60	Time to wait in seconds before retrying the command.	0
Max Tries	0-99	The total number of times the command should attempt to run (including the first attempt).	0

3.5 Workflow Management Tab

• Add path names of tasks and run them in sequence.
• Remove specific tasks or remove them all at once.
• Schedule tasks using the same cron entry.

4. Scheduling

Click the Add Cron Job button. The application will attempt to add the entry to your user's crontab and provide feedback on success or failure through cron emails.

🛑 How the Cron Job is Scheduled

The application updates the crontab by:

1. Fetching the current active crontab using crontab -l.
2. Constructing the new cron job line (using the rf.retry_failures function if retries are enabled).
3. Combining the old crontab content and the new cron job.
4. Piping the entire new content back to the crontab command: echo new_crontab_content | crontab -.

This method ensures that existing cron jobs are preserved.