objective-c NSFilePosixPermissions to human readable NSString
Asked Answered
T

2

6

is there a way to get human readable string (@"drwxr-xr-x" for example) from an NSFilePosixPermissions integer ?

Tasteless answered 8/11, 2010 at 19:15 Comment(3)
Nope. Completely impossible without the Unicorn Talisman and a whole lot of liquor. (See Bitwise Operations: en.wikipedia.org/wiki/Bitwise_operation)Laural
(Up-voted the question since it's a good one and I'm being a smart-a**.) :-)Laural
Thanks Joshua! the accepted answer seems to be fine!Tasteless
H
5

The file system permissions attribute is simply an unsigned long value. The code below could obviously be made more efficient but it shows [more or less] what needs to be done to get the string you want:

// The indices of the items in the permsArray correspond to the POSIX
// permissions. Essentially each bit of the POSIX permissions represents
// a read, write, or execute bit.
NSArray *permsArray = [NSArray arrayWithObjects:@"---", @"--x", @"-w-", @"-wx", @"r--", @"r-x", @"rw-", @"rwx", nil];
NSFileManager *fm = [[[NSFileManager alloc] init] autorelease];
NSMutableString *result = [NSMutableString string];
NSDictionary *attrs = [fm attributesOfItemAtPath:@"some/path.txt" error:NULL];

if (!attrs)
    return nil;

NSUInteger perms = [attrs filePosixPermissions];

if ([[attrs fileType] isEqualToString:NSFileTypeDirectory])
    [result appendString:@"d"];
else
    [result appendString:@"-"];

// loop through POSIX permissions, starting at user, then group, then other.
for (int i = 2; i >= 0; i--)
{
    // this creates an index from 0 to 7
    unsigned long thisPart = (perms >> (i * 3)) & 0x7;

    // we look up this index in our permissions array and append it.
    [result appendString:[permsArray objectAtIndex:thisPart]];
}

return result;
Heuser answered 8/11, 2010 at 20:46 Comment(0)
L
0

Well I guess you can create an array like so:

NSArray *convertToAlpha = [NSArray arrayWithObjects:@"---",@"--x",@"-w-",@"--wx",@"r--",@"r-x",@"rw-",@"rwx", nil];

Then after tranlating the NSFilePosixPermissions to octal, split the resulting number into its componenet digits and use convertToAlpha to map each digit to its alphanumeric representation....

Languedoc answered 8/11, 2010 at 19:35 Comment(2)
xm... I'll try that. I'll get back if I make it, to post the entire solution. Thank you!Tasteless
@VassilisGr, @ennuikiller: beware though, you need an @ symbol behind each string, and also need to add nil to your list of arguments.Heuser

© 2022 - 2024 — McMap. All rights reserved.