Brendan OConnor Brendan OConnor - 3 months ago 23
Scala Question

Read entire file in Scala?

What's a simple and canonical way to read an entire file into memory in Scala? (Ideally, with control over character encoding.)

The best I can come up with is:

scala.io.Source.fromPath("file.txt").getLines.reduceLeft(_+_)


or am I supposed to use one of Java's god-awful idioms, the best of which (without using an external library) seems to be:

import java.util.Scanner
import java.io.File
new Scanner(new File("file.txt")).useDelimiter("\\Z").next()


From reading mailing list discussions, it's not clear to me that scala.io.Source is even supposed to be the canonical I/O library. I don't understand what its intended purpose is, exactly.

... I'd like something dead-simple and easy to remember. For example, in these languages it's very hard to forget the idiom ...

Ruby open("file.txt").read
Ruby File.read("file.txt")
Python open("file.txt").read()

Answer
val lines = scala.io.Source.fromFile("file.txt").mkString

By the way, "scala." isn't really necessary, as it's always in scope anyway, and you can, of course, import io's contents, fully or partially, and avoid having to prepend "io." too.

The above leaves the file open, however. To avoid problems, you should close it like this:

val source = scala.io.Source.fromFile("file.txt")
val lines = try source.mkString finally source.close()

Another problem with the code above is that it is horrible slow due to its implementation nature. For larger files one should use:

source.getLines mkString "\n"
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