Objective-C: Enable/Disable File Reading (chmod a-r)

Question

使用Objective-C，我如何授予/获取所有用户读取文件的权限？

我需要与chmod a-r和chmod a+r具有相同效果的东西.

谢谢！

Answer 1

您是否也熟悉更改权限的chmod 755 file方法？ 使用八进制数字？

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init]; 
//Prefixing zero is octal.
int readPermission = 04;
int writePermission = 02;
int executePermission = 01;
//End multiplication is to shift digits left.
int owner = (readPermission | writePermission | executePermission) * (8 * 8);   //7
int group = (readPermission)                                       * (8);       //4 
int other = (executePermission);                                                //1
int permissions = owner + group + other;  //0741
[dict setObject:[NSNumber numberWithInt:permissions] forKey:NSFilePosixPermissions]; 
NSError *error = nil;
[[NSFileManager defaultManager] setAttributes:dict ofItemAtPath:[file path] error:&error];

Answer 2

要在目标 C 中执行此操作：

NSFileManager *fm = [NSFileManager defaultManager];
NSError *error = nil;
NSDict *attribs = [fm attributesOfItemAtPath:[file path] error:&error];
int permissions = [[attribs objectForKey:@"NSFilePosixPermissions"] intValue];
permissions |= (S_IRSUR | S_IRGRP | S_IROTH);
NSDict *newattribs = [NSDict dictionaryWithObject:[NSNumber numberWithInt:permissions]
                                           forKey:NSFilePosixPermissions];
[fm setAttributes:dict ofItemAtPath:[file path] error:&error];

或者，只需获取一个 POSIX 路径（使用 -[NSFileManager fileSystemRepresentationForPath]），并使用 chmod 函数在 C 中执行此操作，这是 chmod 命令行工具使用的，并且可以移植到任何 POSIX 平台。