Automating bash script

You can use this script to create and manage a systemd-based service to automate running a bash script based on systemd timers.

# Project tree
/ automating-bash-script
  |__ create-service.sh (create and start systemd-based service)
  |__ delete-service.sh (stop and delete systemd-based service)
  |__ memchecker.service.stub (systemd-based service stub)
  |__ memchecker.timer (systemd-based timer)
  |__ memory-checker.sh (the example bash script to be automated)

The example bashscript (memory-checker.sh)

The memory-checker.sh reads memory status from /proc/meminfo, calculates the allocated memory and if the allocated memory exceeded mem_exceed_limit value in /etc/default/memchecker env file, it logs a message to /var/log/memchecker/usage.log

Env file (/etc/default/memchecker)

The below variable means that the memory-checker.sh will log any memory usage above 50% To the /var/log/memchecker/usage.log
You can totaly change this to any number between 1 and 100

mem_exceed_limit=50 # 50%

See, quite uncomplicated example for a bash script!

Create and run

The create-service.sh tries to :

1. add a new user named sysbot
2. create a memchecker.service and memchecker.timer inside /lib/systemd/system
3. create env file for memory-checker.sh in /etc/default/memchecker
4. reload systemctl daemon
5. enable and start memchecker.service and memchecker.timer

# to create and run the service
./create-service.sh

Cheking the memchecker status in systemctl

systemctl status memchecker.service

Cheking if memory usage exceeded

sudo tail /var/log/memchecker/usage.log

Stop and delete

Well everything comes to an end !
You can use the delete-service.sh to stop and delete everything done back in create-service.sh.

The delete-service.sh tries to :

1. delete the user sysbot
2. stop and disbale memchecker.service and memchecker.timer
3. remove memchecker.service and memchecker.timer from /lib/systemd/system
4. reload systemctl daemon

# to stop and delete the service
./delete-service.sh