NSString *file = @"/var/mobile/Library/AppName/interval.txt";
    NSFileManager *manager = [NSFileManager defaultManager];
    NSDictionary *dict;
    dict = [NSDictionary dictionaryWithObjectsAndKeys:
                                  @"/opt/picture.png", @"Luca",
                                  @"/home/nico/birthday.png", @"Birthday Photo",
                                  @"/home/nico/birthday.png", @"Birthday Image",
                                  @"/home/marghe/pic.jpg", @"My Sister",
            nil];

    NSString *err = nil;
    NSData *data;
    data = [NSPropertyListSerialization dataFromPropertyList:dict
                                                      format:NSPropertyListBinaryFormat_v1_0
                                                    errorDescription:&err];
    if([manager fileExistsAtPath:file] == NO){
        [manager createFileAtPath:file contents:data attributes:nil];
    }