Error: md5sum: stat '>': No such file or directory - linux

Question

I am trying to write a program that runs the Linux commands using Scala.
I have written a snippet of code to run the functionalities of md5sum command.
Code snippet
object Test extends App {
import sys.process._
case class md5sum_builder private(i: Seq[String]) {
println(i)
protected def this() = this(Seq(""))
def optionCheck() = new md5sum_builder(i :+ "-c")
def files(file: String) = new md5sum_builder(i :+ file)
def hashFile(hashfile: String) = new md5sum_builder(i :+ hashfile)
def assignment(operator: String) = new md5sum_builder(i :+ operator)
def build() = println(("md5sum" + i.mkString(" ")).!!)
}
object md5sum_builder {
def apply() = new md5sum_builder
}
md5sum_builder().files("text.txt").files("text1.txt").assignment(">").hashFile("hashes.md5").build()
}
When I try to run the command md5sum text.txt text1.txt > hashes.md5 using this program, it throws the error:
Error: md5sum: stat '>': No such file or directory
I don't know why. Any way to make it work?

Answer 1

Your interface doesn't appear to be well thought out. Notice that files(), hashFile(), and assignment() all do the same thing. So someone could come along and do something like this ...
md5sum_builder().assignment("text0.txt")
.hashFile("text1.txt")
.files(">") // <--shell redirection won't work
.assignment("hashes.md5")
.build()
... and get the same (non-functional) result as your posted example.
Here's a modification that corrects for that as well as allowing redirected output.
case class md5sum_builder private(i :Seq[String], outfile :String = "/dev/null") {
protected def this() = this(Seq.empty[String])
def optionCheck(file :String) = this.copy(i = i ++ Seq("-c", file))
def file(file: String) = this.copy(i = i :+ file)
def hashFile(file: String) = this.copy(outfile = file)
def build() = println(("md5sum" +: i).#|(Seq("tee", outfile)).!!)
}
Now the methods can be in almost any order and still get the expected results.
md5sum_builder().file("text0.txt")
.hashFile("hashes.md5")
.file("text1.txt")
.build()