Objective-c NSFilePosixPermissions 到人类可读的 NSString

发布于 2024-10-01 09:08:46 字数 67 浏览 9 评论 0原文

有没有办法从 NSFilePosixPermissions 整数获取人类可读的字符串（例如@“drwxr-xr-x”）？

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踏雪无痕 2024-10-08 09:08:46

文件系统权限属性只是一个无符号长整型值。下面的代码显然可以变得更高效，但它[或多或少]显示了需要做什么才能获得您想要的字符串：

// 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;

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;

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清音悠歌 2024-10-08 09:08:46

好吧，我想你可以像这样创建一个数组：

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

然后将 NSFilePosixPermissions 转换为八进制后，将结果数字拆分为其组件数字，并使用 ConvertToAlpha 将每个数字映射到其字母数字表示形式......

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....

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