Scripts provide a way to run simple scripts inside the framework context, but outside of the usual web request/response lifecycle.
Common use-cases include:
- Sending periodic email reminders
- Sending invoices
- Anything to be run as a cronjob
- Background job-queue processing
Creating a new script
Scripts are located in the
Application/Script/ directory. You can create a new script by running e.g.
new-script HelloWorldToAllUsers. This will create a file at
Application/Script/HelloWorldToAllUsers.hs like this:
#!/usr/bin/env run-script module Application.Script.HelloWorldToAllUsers where import Application.Script.Prelude run :: Script run = do
run function is our entry point. There we can write our logic, just like inside an action. This means we can call other framework functions, access the database using the usual way, send emails, render views, etc.
Let’s print out a hello world to all our users in the console:
#!/usr/bin/env run-script module Application.Script.HelloWorldToAllUsers where import Application.Script.Prelude run :: Script run = do users <- query @User |> fetch forEach users \user -> do putStrLn $ "Hello World, " <> get #firstname user <> "!"
This will fetch all users and then print out “Hello World, Firstname!”.
Running a script
Scripts are executable by default. You can just run them like a bash script:
./Application/Script/HelloWorldToAllUsers.hs ... Hello World, A! Hello World, B! Hello World, C!
This is made possible because of the she-bang line
#!/usr/bin/env run-script at the top of the task file.
In case you get a permission error, try to add the executable flag via
chmod +x Application/Script/HelloWorldToAllUsers.hs.
Building a script
In production, you might want to build a script to a binary for performance reasons. Use make like this:
This will produce a binary
build/bin/Script/HelloWorldToAllUsers from the source file