iOS: "open: Permission denied"

Question

First of all excuse me for my english. This is my first question here. I have read a lot of solutions to both common and uncommon problems on stackoverflow and IMO stackoverflow's community is the most trustful in the branch.

Currently I am developing an iOS application and recently I've encountered a problem and after some research I didn't find solution. When I am using fopen to open existing file I am getting the following error:

open: Permission denied

The following is the code snipped which causes the error:

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *cachePath = [paths objectAtIndex:0];
BOOL isDir = NO;
NSError *error;
if (! [[NSFileManager defaultManager] fileExistsAtPath:cachePath
                                           isDirectory:&isDir] && isDir == NO) {

        [[NSFileManager defaultManager] createDirectoryAtPath:cachePath 
                                  withIntermediateDirectories:NO
                                                  attributes:nil
                                                       error:&error];
}        

NSString* filePath = [cachePath stringByAppendingPathComponent:
                                [NSString stringWithFormat:@"tmpmem%i.bin", count++]];

const char *cPath = [filePath cStringUsingEncoding:NSISOLatin1StringEncoding];

int file = open(cPath, O_RDWR | O_CREAT);

if (file == -1)
{
    perror("open");
    return NULL;
}

I am looking forward for your help. Thank you in advance.

Regards, B. Dimitrov

its hard to know without know what buffer is? all your paths should be relative to [NSBundle mainBundle] — j_mcnally, Mar 05 '12 at 21:22
i'll bow out at this point, i am not really familiar with Cache directories. Is it possible system is taking ownership of things created here? Is there some sort of article or KB that would lead your to believe this should work? — j_mcnally, Mar 05 '12 at 23:29
Also are you re-inventing the wheel, have you looked at core data? — j_mcnally, Mar 05 '12 at 23:31
I have checked the path contained in filePath and it's actually in the bundle. I believed this should work according to http://stackoverflow.com/questions/1567134/how-can-i-get-a-writable-path-on-the-iphone — B. Dimitrov, Mar 05 '12 at 23:55

score 2 · Answer 1 · answered Mar 05 '12 at 21:19

2

Most likely there is nothing wrong with your application. Common causes of this error include lack of search permission for a directory on the path to the file named by cPath, lack of permission to open the file for reading or writing (since you request both with O_RDWR) or the file doesn't exist and the permission to write to the directory in which it should be created is lacking (since you request file creation in case it doesn't exist with O_CREAT).

You should inspect the file and the pathname and ensure all necessary permissions are appropriately set.

answered Mar 05 '12 at 21:19

Adam Zalcman

26,643
4
71
92

Yes you may be outside your sandbox – j_mcnally Mar 05 '12 at 21:20
I have updated the code snipped with the way I find a writable directory. I am able to create the file and write to it but when I close it and try to open it again a get the error. – B. Dimitrov Mar 05 '12 at 21:33

score 0 · Accepted Answer · answered Mar 06 '12 at 19:26

Problem solved. I checked the posix permissions of the folder and they were 493, then I set them to 975 and everything is working as expected. One new question arised: what 9 means in posix permissions since the flags are 4 (Read), 2 (Write) and 1 (Execute)?

iOS: "open: Permission denied"

2 Answers2