How do I create a temporary file with Cocoa?

Question

Years ago when I was working with C# I could easily create a temporary file and get its name with this function:

Path.GetTempFileName();

This function would create a file with a unique name in the temporary directory and return the full path to that file.

In the Cocoa API's, the closest thing I can find is:

NSTemporaryDirectory

Am I missing something obvious or is there no built in way to do this?

Answer 1

You could use mktemp to get a temp filename.

Answer 2

A safe way is to use mkstemp(3).

Answer 3

[Note: This applies to the iPhone SDK, not the Mac OS SDK]

From what I can tell, these functions aren't present in the SDK (the unistd.h file is drastically pared down when compared to the standard Mac OS X 10.5 file). I would use something along the lines of:

[NSTemporaryDirectory() stringByAppendingPathComponent: [NSString stringWithFormat: @"%.0f.%@", [NSDate timeIntervalSinceReferenceDate] * 1000.0, @"txt"]];

Not the prettiest, but functional

Answer 4

You could use an NSTask to uuidgen to get a unique file name, then append that to a string from NSTemporaryDirectory(). This won't work on Cocoa Touch. It is a bit long-winded though.

Answer 5

Though it's nearly a year later, I figured it's still helpful to mention a blog post from Cocoa With Love by Matt Gallagher. http://cocoawithlove.com/2009/07/temporary-files-and-folders-in-cocoa.html He shows how to use mkstemp() for files and mkdtemp() for directories, complete with NSString conversions.

Answer 6

I created a pure Cocoa solution by way of a category on NSFileManager that uses a combination of NSTemporary() and a globally unique ID.

Here the header file:

@interface NSFileManager (TemporaryDirectory)

-(NSString *) createTemporaryDirectory;

@end

And the implementation file:

@implementation NSFileManager (TemporaryDirectory)

-(NSString *) createTemporaryDirectory {
 // Create a unique directory in the system temporary directory
 NSString *guid = [[NSProcessInfo processInfo] globallyUniqueString];
 NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:guid];
 if (![self createDirectoryAtPath:path withIntermediateDirectories:NO attributes:nil error:nil]) {
  return nil;
 }
 return path;
}

@end

This creates a temporary directory but could be easily adapted to use createFileAtPath:contents:attributes: instead of createDirectoryAtPath: to create a file instead.