How do I read a file from the filesystem in a Swift command line app?

Question

I'm just starting learning Swift and to teach myself I'm making a simple command line app. It will eventually connect to an online data source but initially I want to load data from a file. I've seen various guides on reading the contents of a file in Swift but none of them seem to work for me. Here is my app so far:

import Foundation

// Set the file path
let path = "/Users⁩/username/workspace⁩/⁨Swift⁩/sis⁩/sis/data.json⁩"

do {
    // Get the contents
    let contents = try String(contentsOfFile: path, encoding: .utf8)
    print(contents)
}
catch let error as NSError {
    print("Ooops! Something went wrong: \(error)")
}

Running it outputs:

Ooops! Something went wrong: Error Domain=NSCocoaErrorDomain Code=260 "The file “data.json⁩” couldn’t be opened because there is no such file." UserInfo={NSFilePath=/Users⁩/username/workspace⁩/⁨Swift⁩/sis⁩/sis/data.json⁩, NSUnderlyingError=0x100e19a50 {Error Domain=NSPOSIXErrorDomain Code=2 "No such file or directory"}}

However on the terminal:

$ ls -l /Users/username/workspace/Swift/sis/sis/data.json
-rwxrwxrwx@ 1 username  staff  165563 16 Jan 17:14 /Users/username/workspace/Swift/sis/sis/data.json

(yeah I relaxed the permissions somewhat just in case that was the problem)

The only slightly anomalous thing I noticed (aside from the inaccurate assertion that the file doesn't exist) was that when I copy and past the path from the XCode output into iTerm2 it puts spaces between each path component:

(pasted as an image as copying it and pasting it back into this form seems to hide the spaces - this is probably irrelevant anyway)

Any help figuring this out would be really appreciated!

Answer 1

I copied your code, downloaded a sample json file to my desktop, and renamed it to example_ 1.json (I included a space inside the file name).

import Foundation

// Set the file path
let path = "/Users⁩/username/Desktop/example_ 1.json⁩"

do {
    // Get the contents
    let contents = try String(contentsOfFile: path, encoding: .utf8)
    print(contents)
}
catch let error as NSError {
    print("Ooops! Something went wrong: \(error)")
}

It successfully printed the file. It also worked when I defined contents as a NSString.

let contents = try NSString(contentsOfFile: path, 
                            encoding: String.Encoding.ascii.rawValue)

I am using Swift 4.2.1

Answer 2

you can not read if your command line app is sandboxed. what you can do is to add this file in your project and set path of file by looking the full path of file in identity inspector.

let path = "/Users/snx/EmailReplacer/EmailReplacer/shared_domains_staging.json"
do {
    let data = try Data(contentsOf: URL(fileURLWithPath: path), options: .mappedIfSafe)
    let jsonResult = try JSONSerialization.jsonObject(with: data, options: .mutableLeaves)
    if let jsonResult = jsonResult as? Dictionary<String, AnyObject> {
        print(jsonResult)
    }
} catch {
    print(error)
}