school-bell

Cron based command line school-bell alarm system for linux, playing custom audio files as alarm ringtones.

Dependencies

• linux OS (ubuntu tested)
• root permission for install and uninstall
• mplayer installed sudo apt install mplayer
• network connection to keep system time in sync
• correctly configured system timezone
• user who installed school-bell must be logged in to keep scheduled alarms active
• crontab shouldn't be used for other purposes for the specific user

Installation

Execute next command in a linux terminal:

1. clone repository: git clone https://github.com/liszi/school-bell.git
2. enter downloaded folder: cd school-bell
3. start install script: ./install.sh
4. enter a password for root permission when script asks for it

Quickstart

After the successful installation, you can test the school-bell alarm with enabling the sample per-minute schedule with executing the next command in terminal:

crontab ~/school-bell/schedules/sample-schedule-every-minute.cron

It should play default school-bell ringtone every minute.

To disable the alarm, run crontab -r

Check the sample school-bell schedule at ~/school-bell/schedules/sample-school-bell-schedule.cron, edit as expected, and activate it with the next command:

crontab ~/school-bell/schedules/sample-school-bell-schedule.cron

Installed files

~/school-bell folder

After installation, in the home directory of the installer user the school-bell folder will appear. This folder contains all the data and logs for the school-bell application.

~/school-bell/ringtones folder

This folder contains all the ringtones for school-bell application. Any audio file can be copied here which can be played by mplayer. (e.g. mp3, wav, ogg...)

ring command will find any audio file in this folder based on filename (without full path).

~/school-bell/schedules folder

This folder contains all the school-bell schedules. These schedules must be valid linux crontab files with cron extension. These crontab files should utilize ring command with optional ringtones to form a complete school-bell schedule.

For more details see Schedule section.

ring command

Installation process creates a ring command (/usr/bin/ring). This command without arguments plays the default bell ringtone (~/school-bell/ringtones/.default-ringtone.mp3). It accepts one optional parameter, which can be either the full path of a ringtone, or the filename of a ringtone found in ~/school-bell/ringtones/ folder.

Ringtone can be any audio file which can be played with mplayer command.

Logs

ring command generates logs to ~/school-bell/log.txt for each run.

Schedule

Application uses cron for school-bell schedules. Crontab files (*.cron) stores cronjobs, which are periodically running commands.

For school-bell application ring command runs with predefined periods. Each daily school-bell ring event should be a standalone cronjob (line in the crontab file).

To generate linux crontab lines use one of the online crontab generator applications. e.g.:

• https://crontab-generator.org/
• http://www.crontabgenerator.com/
• https://corntab.com/

Let's check part of the ~/school-bell/schedules/sample-school-bell-schedule.cron sample crontab file content:

0 8 * * * ring school-bell-3-seconds.mp3 # Period 1 start ring at 8:00 every day
40 8 * * 1-5 ring school-bell-1-seconds.mp3 # Period 1 alarm ring at 8:40 every weekday
45 8 * * 1-5 ring school-bell-3-seconds.mp3

Each line is representing a cronjob of a daily alarm. First part of the cronjob is defining the timing, with 5 sections (40 12 * * 1-5): minute hours day-of-month month day-of-week. After that ring school-bell-1-seconds.mp3 is the command with the ringtone argument, which plays the ringtone audio with the given timing. After# sign comments can be added to each line.

From more details check cron.

Activate schedule

To activate a specific school-bell schedule, a specific crontab file should be selected with crontab <filepath> command:

With the next command you can activate the sample school-bell schedule:

crontab ~/school-bell/schedules/sample-school-bell-schedule.cron

This will overwrite the previous active crontab.

To see the active schedule, type crontab -l into terminal.

Disable schedule

To stop all the school-bell alarms run crontab -r.

Uninstall

To uninstall an installed school-bell application run ~/school-bell/.uninstall.sh command.

This command will deactivate all the active crontabs, and remove the installed commands from /usr/bin folder.

Uninstall will not remove the school-bell working directory since it can contain important crontabs and ringtones. To remove all the crontabs and ringtones execute rm -r ~/school-bell/ command in terminal manually.

Troubleshooting

Can't hear school-bell ring sound

1. Test your audio with playing some sound if it is working properly.
2. Check your crontab and it's timing if it is configured as expected with executing crontab -l in terminal. You should see the same content as the schedule file *.cron, what you've activated last time. If it is not there, activate it again.
3. mplayer must be installed and available from terminal.
4. User must be logged in to hear the sound.
5. Check ~/school-bell/log.txt file for detailed info.

School-bell ring played instead of my custom audio

When ring command can't find the defined custom audio file, it'll play the default ringtone. Possible reasons:

1. No custom ringtone is not provided after ring command in the active schedule.
2. Provided custom ringtone path is invalid. Provide full path of the ringtone, or copy it to ~/school-bell/ringtones folder and provide only filename.
3. Check ~/school-bell/log.txt file for detailed info.

Incorrect schedule timing

1. Check if the system time is in sync. You need internet connection, and enabled time syncronization to network time (with NTP)
2. Check your system timezone.
3. Check your active schedule with crontab -l command if it is the expected.