从文件中抓取随机行

I have no idea on how to do this. Where should I start? I have googled this and not one result came up on how to pull a random line from a text file.

我不知道如何做到这一点。我应该从哪里开始？我用谷歌搜索了这个，并没有提出如何从文本文件中拉出随机行的结果。

The only thing I have found is https://github.com/chrisinajar/node-rand-line, however it doesn't work. How can I read a random line from a text file?

我发现的唯一的东西是https://github.com/chrisinajar/node-rand-line，但它不起作用。如何从文本文件中读取随机行？

3 个解决方案

#1

You would probably want to look at the node.js standard library function for reading files, fs.readFile, and end up with something along the lines of:

您可能希望查看node.js标准库函数来读取文件fs.readFile，最后得到以下内容：

//note this will be async
function getRandomLine(filename){
  fs.readFile(filename, function(err, data){
    if(err) throw err;
    var lines = data.split('\n');
    /*do something with */ lines[Math.floor(Math.random()*lines.length)];
 })
}

If reading the whole thing and splitting isn't an option, then maybe have a look at this stack overflow for ideas.

如果阅读整个事情并且拆分不是一个选项，那么可能要看看这个堆栈溢出的想法。

#2

I don't have Node handy to test code, so I can't give you exact code, but I would do something like this:

我没有Node方便测试代码，所以我不能给你确切的代码，但我会做这样的事情：

Get the file size in bytes, pick a random byte offset
获取文件大小（以字节为单位），选择随机字节偏移量
Open the file as a stream
以流形式打开文件
Use this snippet to emit lines (or readline, but last I used it had a nasty bug where it essentially didn't work)
使用这个片段发出行（或readline，但最后我使用它有一个讨厌的bug，它本质上不起作用）
Keep track of your position in the file as you read. As you pass your chosen offset, select that line and return it.
在阅读时跟踪您在文件中的位置。当您传递所选的偏移量时，选择该行并将其返回。

Note that this isn't entirely random. Longer lines will be weighted more heavily, but it is the only way to do it without reading the whole file to get a count of lines.

请注意，这并非完全随机。较长的行将被加权更多，但它是唯一的方法，无需读取整个文件来获得行数。

This method allows you to get a "random" line without keeping the whole file in memory.

此方法允许您获取“随机”行而不将整个文件保留在内存中。

#3

I can give you a suggestion as I don't have any demo code

我可以给你一个建议，因为我没有任何演示代码

Read the file line by line using buffered reader
使用缓冲读取器逐行读取文件
Store every line in a String array
将每一行存储在String数组中
Create a method int returnRandom(arraySize)
创建方法int returnRandom（arraySize）
Pass the array size in to the function
将数组大小传递给函数
Calculate a random number between 0 to arraySize
计算0到arraySize之间的随机数
Return the random number
返回随机数
Print the given index from your string array
从字符串数组中打印给定的索引

#1