NSTemporaryDirectory 临时文件

 NSString*identifier=[[NSProcessInfoprocessInfo]globallyUniqueString];

NSString *fileName=[NSStringstringWithFormat:@"%@_%@", [[NSProcessInfoprocessInfo] globallyUniqueString], @"file.txt"];

NSURL *fileURL=[NSURLfileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:fileName]];

NSURL *directoryURL = [NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:[[NSProcessInfo processInfo] globallyUniqueString]] isDirectory:YES];
[[NSFileManager defaultManager] createDirectoryAtURL:directoryURL withIntermediateDirectories:YES attributes:nil error:&error];

NSData *data = ...;
NSError *error = nil;
[data writeToURL:fileURL options:NSDataWritingAtomic error:&error];

NSOutputStream *outputStream = [NSOutputStream outputStreamToFileAtPath:[fileURL absoluteString] append:NO];

NSError *error = nil;
[[NSFileManager defaultManager] removeItemAtURL:fileURL error:&error];