Question

Does anybody know whether there’s a way of finding out whether a particular file system location is accessible under the sandbox?

I want to test whether a particular file is accessible under the normal Powerbox rules; that is has already been added to the power box using the open/ save dialog, etc.

Can I do this before triggering a sandbox exception?

Can I catch a sandbox exception?

Best regards,

Frank

Answer 1

You can use the OS access() system call for a quick and simple test, from man access:

#include <unistd.h>

int access(const char *path, int amode);

The access() function checks the accessibility of the file named by path
for the access permissions indicated by amode. The value of amode is the
bitwise inclusive OR of the access permissions to be checked (R_OK for
read permission, W_OK for write permission and X_OK for execute/search
permission) or the existence test, F_OK. All components of the pathname
path are checked for access permissions (including F_OK).

If path cannot be found or if any of the desired access modes would not
be granted, then a -1 value is returned and the global integer variable
errno is set to indicate the error. Otherwise, a 0 value is returned.

You could pretty this up for Objective-C using something like:

typedef enum
{
   ReadAccess = R_OK,
   WriteAccess = W_OK,
   ExecuteAccess = X_OK,
   PathExists = F_OK
} AccessKind;


BOOL isPathAccessible(NSString *path, AccessKind mode)
{
   return access([path UTF8String], mode) == 0;
}