Scala: write string to file in one statement

Question

For reading files in Scala, there is

Source.fromFile(\"file.txt\").mkString

Is there an equivalent and concise way to write a string to fi

Answer 1

If you like Groovy syntax, you can use the Pimp-My-Library design pattern to bring it to Scala:

import java.io._
import scala.io._

class RichFile( file: File ) {

  def text = Source.fromFile( file )(Codec.UTF8).mkString

  def text_=( s: String ) {
    val out = new PrintWriter( file , "UTF-8")
    try{ out.print( s ) }
    finally{ out.close }
  }
}

object RichFile {

  implicit def enrichFile( file: File ) = new RichFile( file )

}

It will work as expected:

scala> import RichFile.enrichFile
import RichFile.enrichFile

scala> val f = new File("/tmp/example.txt")
f: java.io.File = /tmp/example.txt

scala> f.text = "hello world"

scala> f.text
res1: String = 
"hello world

Answer 2

One also has this format, which is both concise and the underlying library is beautifully written (see the source code):

import scalax.io.Codec
import scalax.io.JavaConverters._

implicit val codec = Codec.UTF8

new java.io.File("hi-file.txt").asOutput.write("I'm a hi file! ... Really!")

Answer 3

You can do this with a mix of Java and Scala libraries. You will have full control over the character encoding. But unfortunately, the file handles will not be closed properly.

scala> import java.io.ByteArrayInputStream
import java.io.ByteArrayInputStream

scala> import java.io.FileOutputStream
import java.io.FileOutputStream

scala> BasicIO.transferFully(new ByteArrayInputStream("test".getBytes("UTF-8")), new FileOutputStream("test.txt"))

Answer 4

A concise one line:

import java.io.PrintWriter
new PrintWriter("filename") { write("file contents"); close }

Answer 5

import sys.process._
"echo hello world" #> new java.io.File("/tmp/example.txt") !

Answer 6

UPDATE: I have since created a more effective solution upon which I have elaborated here: https://stackoverflow.com/a/34277491/501113

I find myself working more and more in the Scala Worksheet within the Scala IDE for Eclipse (and I believe there is something equivalent in IntelliJ IDEA). Anyway, I need to be able to do a one-liner to output some of the contents as I get the "Output exceeds cutoff limit." message if I am doing anything significant, especially with the Scala collections.

I came up with a one-liner I insert into the top of each new Scala Worksheet to simplify this (and so I don't have to do the whole external library import exercise for a very simple need). If you are a stickler and notice that it is technically two lines, it's only to make it more readable in this forum. It is a single line in my Scala Worksheet.

def printToFile(content: String, location: String = "C:/Users/jtdoe/Desktop/WorkSheet.txt") =
  Some(new java.io.PrintWriter(location)).foreach{f => try{f.write(content)}finally{f.close}}

And the usage is simply:

printToFile("A fancy test string\ncontaining newlines\nOMG!\n")

This allows me to optionally provide the file name should I want to have additional files beyond the default (which completely overwrites the file each time the method is called).

So, the second usage is simply:

printToFile("A fancy test string\ncontaining newlines\nOMG!\n", "C:/Users/jtdoe/Desktop/WorkSheet.txt")

Enjoy!