Get domain name from dsconfigad

DomainInfo.m

NSString *
getDomainName() {
    // "dsconfigad --show" command returns domain which mac joined to or nothing if mac is not joined to any domain
    NSTask *task = [[NSTask alloc] init];
    [task setLaunchPath:@"/usr/sbin/dsconfigad"];
    [task setArguments: [NSArray arrayWithObjects:@"--show", nil]];
    
    NSPipe *pipe = [NSPipe pipe];
    [task setStandardOutput: pipe];
    
    NSFileHandle *file = [pipe fileHandleForReading];
    
    [task launch];
    [task waitUntilExit];
    
    NSString *string = [[NSString alloc] initWithData: [file readDataToEndOfFile] encoding: NSUTF8StringEncoding];
    
    NSError *err;
    NSRegularExpression *regex = [[NSRegularExpression alloc]
                                  initWithPattern:@"Active Directory Domain\\s+=\\s+(.+)\\s" options:NSRegularExpressionCaseInsensitive error:&err];
    
    if (!err) {
        NSTextCheckingResult *match = [regex firstMatchInString:string
                                                        options:0
                                                          range:NSMakeRange(0, [string length])];
        if(match) {
            if ([match numberOfRanges] > 1) {
                // domain name is first regex group
                NSString *domainName = [string substringWithRange:[match rangeAtIndex:1]];
                
                return domainName;
            }
        }
    }
    
    return nil;
}