How to make an NSString path (file name) safe

Question

I'm using very tricky fighting methods :) to make a string like Fi?le*/ Name safe for using as a file name like File_Name. I'm sure there is a cocoa way to convert it. And I'm sure the best place to ask is here :)

Thank you!

Answer 1

Unless you're explicitly running the shell or implicitly running the shell by using a function such as popen or system, there's no reason to escape anything but the pathname separator.

You may also want to enforce that the filename does not begin with a full stop (which would cause Finder to hide the file) and probably should also enforce that it is not empty and is fewer than NAME_MAX characters* long.

*syslimits.h says bytes, but if you go through File Manager, it's characters. I'm not sure which is right for Cocoa.

Answer 2

According to wikipedia, the most common characters that should be excluded from filenames are:

/\?%*|"<>

http://en.wikipedia.org/wiki/Filename

Given that, and since the invertedSet operation in the alternate solution can be intensive, to me the below is a cleaner approach:

NSCharacterSet *invalidFsChars = [NSCharacterSet characterSetWithCharactersInString:@"/\\?%*|\"<>"];
NSString *scrubbed = [originalStr stringByTrimmingCharactersInSet:invalidFsChars];

This way you can still allow filenames that have dash, etc.

Answer 3

I iterated on johnboiles's answer, converting to Swift, and writing it as an extension:

extension String {
    var stringForFilePath: String {
        // characterSet contains all illegal characters on OS X and Windows
        let characterSet = NSCharacterSet(charactersInString: "\"\\/?<>:*|")
        // replace "-" with character of choice
        return componentsSeparatedByCharactersInSet(characterSet).joinWithSeparator("-")
    }
}

Illegal character set referenced from here.

Answer 4

And of course there's got to be a swift2 guy with an arbitrary hate list (stolen from other answers). That guy is me:

func sanitizedString(string : String) -> String {
    // put anything you dislike in that set ;-)
    let invalidFsChars = NSCharacterSet(charactersInString: "/* <>?%|")
    let components = string.componentsSeparatedByCharactersInSet(invalidFsChars)
    return components.joinWithSeparator("")
}

Answer 5

This will remove all invalid characters anywhere in the filename based on Ismail's invalid character set (I have not verified how complete his set is).

- (NSString *)_sanitizeFileNameString:(NSString *)fileName {
    NSCharacterSet* illegalFileNameCharacters = [NSCharacterSet characterSetWithCharactersInString:@"/\\?%*|\"<>"];
    return [[fileName componentsSeparatedByCharactersInSet:illegalFileNameCharacters] componentsJoinedByString:@""];
}

Credit goes to Peter N Lewis for the idea to use componentsSeparatedByCharactersInSet:
NSString - Convert to pure alphabet only (i.e. remove accents+punctuation)

Answer 6

Solution in Swift 4

extension String {
    var sanitizedFileName: String {
        return components(separatedBy: .init(charactersIn: "/\:\?%*|\"<>")).joined()
    }
}

Usage:

"https://myurl.com".sanitizedFileName // = httpsmyurl.com