在haskell中检索文件大小的最佳方法是什么？ [英] What is the best way to retrieve the size of a file in haskell?

问题描述

我想知道如何以最少的开销获得haskell中文件的大小。现在我有下面的代码：

I am wondering how to get the size of a file in haskell with the least amount of overhead. Right now I have the following code:

getFileSize :: FilePath -> IO Integer
getFileSize x = do
handle <- openFile x ReadMode
size <- hFileSize handle
hClose handle
return size

这似乎很慢。我偶然发现了System.Posix.Files中的getFileStatus，但不知道它是如何工作的 - 至少我在ghci中使用它时只会遇到错误。此外，我不确定这是否会在Windows上工作（可能不是）。

This seems to be quite slow. I have stumbled across getFileStatus in System.Posix.Files but don't know how it works - at least I only get errors when playing around with it in ghci. Also, I am not sure if this would work on Windows (probably not).

所以要重申：什么是最好的（和平台无关的）方法来获得大小在Haskell中的一个文件？

So to reiterate: What is the best (and platform independent) approach to get the size of a file in Haskell?

推荐答案

你想要的确实是 getFileStatus 和 fileSize ，它们都来自 System.Posix （在Windows下它可以正常工作，请注意）。用法如下，错误处理由您决定：

What you want are indeed getFileStatus and fileSize, both from System.Posix (which will work just fine under Windows, mind you). Usage is as follows, leaving error handling up to you:

getFileSize :: String -> IO FileOffset
getFileSize path = do
    stat <- getFileStatus path
    return (fileSize stat)

对于它的价值，虽然我认为它的可读性较差，但可以将此表缩短为：

For what it's worth, and though I think it's less readable, you could shorten this form to:

getFileSize path = getFileStatus path >>= \s -> return $ fileSize s

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