objective-c NSFilePosixPermissions到人類可讀的NSString

Question

是否有一種方法來從NSFilePosixPermissions整數獲取人類可讀的字符串（例如@「drwxr-xr-x」）？

Answer 1

文件系統權限屬性只是一個無符號長整型值。下面的代碼顯然可以提高效率，但它顯示[或多或少]需要做些什麼來獲得所需的字符串：

// 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; 

Answer 2

嗯，我想你可以創建一個數組，像這樣：

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

然後tranlating的NSFilePosixPermissions爲八進制數之後，拆分導致數到它的組元的數字，並使用convertToAlpha映射每一位數字的字母數字表示。 ...