How to export DataFrame to csv in Scala?

Easiest and best way to do this is to use spark-csv library. You can check the documentation in the provided link and here is the scala example of how to load and save data from/to DataFrame.

Code (Spark 1.4+):

dataFrame.write.format("com.databricks.spark.csv").save("myFile.csv")

Edit:

Spark creates part-files while saving the csv data, if you want to merge the part-files into a single csv, refer the following:

Merge Spark's CSV output folder to Single File

In Spark verions 2+ you can simply use the following;

df.write.csv("/your/location/data.csv")

If you want to make sure that the files are no longer partitioned then add a .coalesce(1) as follows;

df.coalesce(1).write.csv("/your/location/data.csv")

Above solution exports csv as multiple partitions. I found another solution by zero323 on this stackoverflow page that exports a dataframe into one single CSV file when you use coalesce.

df.coalesce(1)
  .write.format("com.databricks.spark.csv")
  .option("header", "true")
  .save("/your/location/mydata")

This would create a directory named mydata where you'll find a csv file that contains the results.