How do I create a temporary file with Cocoa? - objective-c

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

A safe way is to use mkstemp(3).

Answer 2

[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 3

Apple has provided an excellent way for accessing temp directory and creating unique names for the temp files.
- (NSString *)pathForTemporaryFileWithPrefix:(NSString *)prefix
{
NSString * result;
CFUUIDRef uuid;
CFStringRef uuidStr;
uuid = CFUUIDCreate(NULL);
assert(uuid != NULL);
uuidStr = CFUUIDCreateString(NULL, uuid);
assert(uuidStr != NULL);
result = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:#"%#-%#", prefix, uuidStr]];
assert(result != nil);
CFRelease(uuidStr);
CFRelease(uuid);
return result;
}
LINK :::: http://developer.apple.com/library/ios/#samplecode/SimpleURLConnections/Introduction/Intro.html#//apple_ref/doc/uid/DTS40009245
see file :::AppDelegate.m

Answer 4

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.

Answer 5

If targeting iOS 6.0 or Mac OS X 10.8 or higher:
NSString *tempFilePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[[NSUUID UUID] UUIDString]];

Answer 6

Swift 5 and Swift 4.2
import Foundation
func pathForTemporaryFile(with prefix: String) -> URL {
let uuid = UUID().uuidString
let pathComponent = "\(prefix)-\(uuid)"
var tempPath = URL(fileURLWithPath: NSTemporaryDirectory())
tempPath.appendPathComponent(pathComponent)
return tempPath
}
let url = pathForTemporaryFile(with: "blah")
print(url)
// file:///var/folders/42/fg3l5j123z6668cgt81dhks80000gn/T/johndoe.KillerApp/blah-E1DCE512-AC4B-4EAB-8838-547C0502E264
Or alternatively Ssswift's oneliner:
let prefix = "blah"
let url2 = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("\(prefix)-\(UUID())")
print(url2)

Answer 7

You could use mktemp to get a temp filename.

Answer 8

The modern way to do this is FileManager's url(for:in:appropriateFor:create:).
With this method, you can specify a SearchPathDirectory to say exactly what kind of temporary directory you want. For example, a .cachesDirectory will persist between runs (as possible) and be saved in the user's library, while a .itemReplacementDirectory will be on the same volume as the target file.

Answer 9

Don't use legacy APIs like NSTemporaryDirectory, get a proper URL instead from FileManager.
let tmpURL = FileManager
.default
.temporaryDirectory
.appendingPathComponent(UUID().uuidString)
You'd still have to create the directory.

Answer 10

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 11

Adding to #Philipp:
- (NSString *)createTemporaryFile:(NSData *)contents {
// Create a unique file in the system temporary directory
NSString *guid = [[NSProcessInfo processInfo] globallyUniqueString];
NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:guid];
if(![self createFileAtPath:path contents:contents attributes:nil]) {
return nil;
}
return path;
}