在Groovy中尾随一个文件 [英] Tail a file in Groovy

问题描述

我想知道是否有一种简单的方式在Groovy中定位文件？我知道如何读取文件，但是如何读取文件，然后等待更多行添加，读取它们，等待等等。

I有什么我肯定是一个非常愚蠢的解决方案：

  def lNum = 0 
 def num = 0 
 def numLines = 0 
 def myFile = new File（foo.txt）
 def origNumLines = myFile.eachLine {num ++} 
 def precIndex = origNumLines 
 
 while（true）{
 num = 0 
 lNum = 0 
 numLines = myFile.eachLine {num ++} 
 
 if（numLines> origNumLines）{
 myFile.eachLine（{line  - > 
 
 if（lNum> precIndex）{
 println line 
} 
 lNum ++ 
}）
 
 precIndex = numLines 
 
 Thread.sleep（5000）
} 
  

请注意，我对调用Unixtail命令并不感兴趣。除非它是唯一的解决方案。

解决方案

我写了一个类似于基本尾部功能的groovy类：
$ b

  class TailReader {
 
 boolean stop = false 
 
 public void stop（）{
 stop = true 
} 
 
 public void tail（File file，Closure c）{
 def runnable = {
 def reader 
 
尝试{
 reader = file.newReader（）
 reader.skip（file.length（））
 
 def line 
 
 while（！stop） {
 line = reader.readLine（）
 if（line）{
 c.call（line）
} 
 else {
 Thread.currentThread（ ）.sleep（1000）
} 
} 
 
} 
 finally {
 reader。.close（）
} 
 } as Runnable 
 
 def t = new Thread（runnable）
 t.start（）
} 
} 
  

tail 方法以文件和闭包作为参数。它将在一个单独的线程中运行，并会将每个新行添加到文件中以传递给给定的闭包。 tail 方法将一直运行，直到在 TailReader stop 方法$ c>实例。下面是一个简单的例子，介绍如何使用 TailReader 类：

  def reader = new TailReader（）
 reader.tail（new File（/ tmp / foo.log））{println it} 
 
 //执行其他操作，例如
 // Thread.currentThread（）。sleep（30 * 1000）
 
 reader.stop（）
  

I am wondering is there is a simple way to tail a file in Groovy? I know how to read a file, but how do I read a file and then wait for more lines to be added, read them, wait, etc...

I have what I am sure is a really stupid solution:

def lNum = 0
def num= 0
def numLines = 0
def myFile = new File("foo.txt")
def origNumLines = myFile.eachLine { num++ }
def precIndex = origNumLines

while (true) {
num = 0
lNum = 0
numLines = myFile.eachLine { num++ }

if (numLines > origNumLines) {
    myFile.eachLine({ line ->

    if (lNum > precIndex) {
            println line
        }
    lNum++
    })
}
precIndex = numLines

 Thread.sleep(5000)
}

Note that I am not really interested in invoking the Unix "tail" command. Unless it is the only solution.

解决方案

I wrote a groovy class which resembles the basic tail functionality:

class TailReader {

  boolean stop = false

  public void stop () {
    stop = true
  }

  public void tail (File file, Closure c) {
    def runnable = {
     def reader

      try {
        reader = file.newReader()
        reader.skip(file.length())

        def line

        while (!stop) {
          line = reader.readLine()
          if (line) {
            c.call(line)
          }
          else {
            Thread.currentThread().sleep(1000)
          }
        }

      }
      finally {
        reader?.close()
      }
    } as Runnable

    def t = new Thread(runnable)
    t.start()
  }
}

The tail method taks a file and closure as parameters. It will run in a separate thread and will pass each new line that will be appended to the file to the given closure. The tail method will run until the stop method is called on the TailReader instance. Here's a short example of how to use the TailReader class:

def reader = new TailReader()
reader.tail(new File("/tmp/foo.log")) { println it }

// Do something else, e.g. 
// Thread.currentThread().sleep(30 * 1000)

reader.stop()

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