在Scala中解析命令行参数的最佳方法是什么? 我个人更喜欢一些不需要外部罐子的轻量级的东西。

相关:

我如何解析Java中的命令行参数? c++有哪些参数解析器库? 在c#中解析命令行参数的最佳方法


当前回答

我已经尝试概括@pjotrp的解决方案,通过在必要的位置键符号的列表,一个映射的标志->键符号和默认选项:

def parseOptions(args: List[String], required: List[Symbol], optional: Map[String, Symbol], options: Map[Symbol, String]): Map[Symbol, String] = {
  args match {
    // Empty list
    case Nil => options

    // Keyword arguments
    case key :: value :: tail if optional.get(key) != None =>
      parseOptions(tail, required, optional, options ++ Map(optional(key) -> value))

    // Positional arguments
    case value :: tail if required != Nil =>
      parseOptions(tail, required.tail, optional, options ++ Map(required.head -> value))

    // Exit if an unknown argument is received
    case _ =>
      printf("unknown argument(s): %s\n", args.mkString(", "))
      sys.exit(1)
  }
}

def main(sysargs Array[String]) {
  // Required positional arguments by key in options
  val required = List('arg1, 'arg2)

  // Optional arguments by flag which map to a key in options
  val optional = Map("--flag1" -> 'flag1, "--flag2" -> 'flag2)

  // Default options that are passed in
  var defaultOptions = Map()

  // Parse options based on the command line args
  val options = parseOptions(sysargs.toList, required, optional, defaultOptions)
}

其他回答

我再多说一点。我用一行简单的代码解决了这个问题。我的命令行参数是这样的:

input--hdfs:/path/to/myData/part-00199.avro output--hdfs:/path/toWrite/Data fileFormat--avro option1--5

这将通过Scala的本机命令行功能(从App或main方法)创建一个数组:

Array("input--hdfs:/path/to/myData/part-00199.avro", "output--hdfs:/path/toWrite/Data","fileFormat--avro","option1--5")

然后我可以使用这一行来解析出默认的args数组:

val nArgs = args.map(x=>x.split("--")).map(y=>(y(0),y(1))).toMap

它创建了一个与命令行值关联的名称映射:

Map(input -> hdfs:/path/to/myData/part-00199.avro, output -> hdfs:/path/toWrite/Data, fileFormat -> avro, option1 -> 5)

然后,我可以在代码中访问命名参数的值,它们在命令行上出现的顺序不再相关。我意识到这相当简单,没有上面提到的所有高级功能,但在大多数情况下似乎足够了,只需要一行代码,并且不涉及外部依赖关系。

Here's a scala command line parser that is easy to use. It automatically formats help text, and it converts switch arguments to your desired type. Both short POSIX, and long GNU style switches are supported. Supports switches with required arguments, optional arguments, and multiple value arguments. You can even specify the finite list of acceptable values for a particular switch. Long switch names can be abbreviated on the command line for convenience. Similar to the option parser in the Ruby standard library.

另一个库:scarg

我喜欢这段代码的简洁外观…从这里的讨论中收集到: http://www.scala-lang.org/old/node/4380

object ArgParser {
  val usage = """
Usage: parser [-v] [-f file] [-s sopt] ...
Where: -v   Run verbosely
       -f F Set input file to F
       -s S Set Show option to S
"""

  var filename: String = ""
  var showme: String = ""
  var debug: Boolean = false
  val unknown = "(^-[^\\s])".r

  val pf: PartialFunction[List[String], List[String]] = {
    case "-v" :: tail => debug = true; tail
    case "-f" :: (arg: String) :: tail => filename = arg; tail
    case "-s" :: (arg: String) :: tail => showme = arg; tail
    case unknown(bad) :: tail => die("unknown argument " + bad + "\n" + usage)
  }

  def main(args: Array[String]) {
    // if there are required args:
    if (args.length == 0) die()
    val arglist = args.toList
    val remainingopts = parseArgs(arglist,pf)

    println("debug=" + debug)
    println("showme=" + showme)
    println("filename=" + filename)
    println("remainingopts=" + remainingopts)
  }

  def parseArgs(args: List[String], pf: PartialFunction[List[String], List[String]]): List[String] = args match {
    case Nil => Nil
    case _ => if (pf isDefinedAt args) parseArgs(pf(args),pf) else args.head :: parseArgs(args.tail,pf)
  }

  def die(msg: String = usage) = {
    println(msg)
    sys.exit(1)
  }

}

我刚刚在scalac的scala.tools.cmd包中找到了一个广泛的命令行解析库。

参见http://www.assembla.com/code/scala-eclipse-toolchain/git/nodes/src/compiler/scala/tools/cmd?rev=f59940622e32384b1e08939effd24e924a8ba8db