schedule_scraper.md

This is a brief explanation on how to schedule a task to run on each log on.

Linux

Since the cron utility does not offer ONLOGON option (or I could not figure out how), the simplest way I found was:

1. make a small bash script...
   sudo gedit packt_scraper_schtask.sh

2. ...containing the following 3 lines...

   #!/bin/bash
   
   sleep 180
   /usr/bin/Rscript ~/projects/packt-scraper/R/check_and_run_scraper.R
   

3. give it permissions...
   chmod +x packt_scraper_schtask.sh

4. ...and add it to the startup applications in gnome-sessions-properties.

I followed the approach outlined in this answer and it worked for me.
The task itself has a 3 minute delay - which means the notification should pop up 3 minutes after login.

Windows

The windows task scheduler utility does have a ONLOGON option which makes it even easier and we can do everything from withing R itself.

# of course there is already an R package for this
if (!require("taskscheduleR"))
  install.packages("taskscheduleR")
library("taskscheduleR")

# path to Rscript
rscript_exe <- file.path( R.home(), "bin", "Rscript.exe" )

# path to the check-and-run script
proj_dir <- # getwd()  # if you cloned this as Rproj
script_path <- file.path(proj_dir, "check_and_run_scraper.R")

# schedule script to run
taskscheduleR::taskscheduler_create(taskname = "packt_book_scraper",
                                    rscript = script_path,
                                    schedule = "ONLOGON",
                                    Rexe = rscript_exe,
                                    starttime = Sys.Date()
                                    )