A great thing about Scala is that not only is it scalable, it was also created to help you work on small tasks, including being useful in shell scripts. This includes small shell script tasks like prompting a user interactively from a shell script, and reading their input.
You can prompt users with print commands like
- readLine - lets you prompt a user and read their input as text
(There's also a
readf method that lets you read formatted (structured) input, which I'll demonstrate in a future Scala tutorial.)
An example shell script
The Scala shell script shown here demonstrates several techniques you can use to (a) prompt users with your output and (b) read their input. I've added comments to the shell script, so I won't describe it beforehand:
#!/bin/sh exec scala -savecompiled "$0" "$@" !# // write some text out to the user with Console.print Console.println("Hello") // Console is imported by default, so it's not really needed, just use println println("World") // readLine: lets you prompt the user and also read their command line input val name = readLine("What's your name? ") // readInt: read a simple Int print("How old are you? ") val age = readInt() // you can also print output with printf printf("Your name is %s and you are %d years old.\n", name, age) // you can also use the Java Scanner class, if desired val scanner = new java.util.Scanner(System.in) print("Where do you live? ") val input = scanner.nextLine() print("You live in " + input)
I hope those comments provide enough explanation for how Scala command line input and output works. I encourage you to copy these commands into your own shell script, run it, and then see how everything works. (You'll quickly see that you'll want to add some error-checking to your script, especially the readInt() method.)
If the lines at the top of this shell script seem a little unusual, check out my previous Scala shell script tutorials, where those lines are explained:
- Scala shell script syntax examples
- How to make your Scala shell scripts run faster with the "savecompiled" argument
I hope this Scala shell script example on prompting a user for input and then reading their input has been helpful. For many more Scala tutorials, see my Scala cookbook/recipes page.
For more examples on how to prompt users and read their input, see my “How to prompt users for input from Scala shell scripts” tutorial.
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