在Swift中将NSLog重定向到File无法正常工作 [英] Redirect NSLog to File in Swift not working

问题描述

我正在尝试将NSLog发送到在Simulator，IOS 10.2上运行的Swift 3中的文件，并且没有生成任何内容

I am trying to send NSLog to a file in Swift 3 running on Simulator, IOS 10.2 and nothing is being produced

如何将NSLog转换为文件

func redirectConsoleLogToDocumentFolder() {
    let file = "file.txt"
    if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {

        let logPath = dir.appendingPathComponent(file).absoluteString
        print("log:\(logPath)")
        freopen(logPath, "a+", stderr)
    }
    NSLog("print nslog")
}

输出

~/Library/Developer/CoreSimulator/Devices/A7B717-3ED8-493A-9778-C594AF9FF446/data/Containers/Data/Application/B0386-64BB-46EB-9BF2-65209FC748CD/Documents/file.txt

唯一的影响是输出不再打印到控制台。

The only effect is that the output is no longer printed to the console.

我试过

freopen(logPath.cString(using: .utf8), "a+", stderr)

以及其他各种组合

使用我的路径写一个文件我没有问题接收所以没有任何问题

I have no trouble writing to a file with the path I am receiving so there is nothing wrong with that

我希望在路径中看到一个名为file.txt的文件，并且文件包含print nslog。我尝试先创建文件但没有成功。

I expected to see a file created called file.txt in the path and the file to contains "print nslog". I have tried creating the file first without success.

推荐答案

absoluteString URL的属性生成一个URL字符串，例如

The absoluteString property of an URL produces an URL string, e.g.

    file:///path/to/file.txt

这不适合作为 freopen（）的参数。
要将文件路径作为字符串，请改为使用路径：

let logPath = dir.appendingPathComponent(file).path

更好，使用专用方法将URL路径传递给系统调用：

Better, use the dedicated method to pass an URLs path to a system call:

let logFileURL = dir.appendingPathComponent(file)
logFileURL.withUnsafeFileSystemRepresentation {
    _ = freopen($0, "a+", stderr)
}

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