为什么(有时)为我的服务创建的文件设置只读属性?

注意:这是对这个问题的完整重写。我之前曾将一些ACL问题与我正在寻找的问题混为一谈,这可能是没有答案的原因。

我有一个windows服务,它使用标准的打开/关闭/写入例程来写入日志文件(它从管道中读取内容并将其写入日志)。每天午夜都会打开一个新的日志文件。该系统为Windows XP嵌入式系统。

当服务最初启动时,它会创建一个日志文件并写入其中,没有任何问题。此时一切正常,您可以毫无问题地重新启动服务(或计算机)。

 Directory of C:\bbbaudit

09/16/2009  12:00 AM    <DIR>          .
09/16/2009  12:00 AM    <DIR>          ..
09/16/2009  12:00 AM               437 AU090915.ADX
09/16/2009  12:00 AM                62 AU090916.ADX

attrib c:\bbbaudit\*
A          C:\bbbaudit\AU090915.ADX <-- old log file (before midnight)
A    R     C:\bbbaudit\AU090916.ADX <-- new log file (after midnight)

cacls output:
C:\ BUILTIN\Administrators:(OI)(CI)F 
    NT AUTHORITY\SYSTEM:(OI)(CI)F 
    CREATOR OWNER:(OI)(CI)(IO)F 
    BUILTIN\Users:(OI)(CI)R 
    BUILTIN\Users:(CI)(special access:)
                      FILE_APPEND_DATA

    BUILTIN\Users:(CI)(IO)(special access:)
                          FILE_WRITE_DATA

    Everyone:R 

C:\bbbaudit BUILTIN\Administrators:(OI)(CI)F 
            NT AUTHORITY\SYSTEM:(OI)(CI)F 
            CFN3\Administrator:F 
            CREATOR OWNER:(OI)(CI)(IO)F 

以下是我用来打开/创建日志文件的代码:

static int open_or_create_file(char *fname, bool &alreadyExists)
{
  int fdes;

  // try to create new file, fail if it already exists
  alreadyExists = false;
  fdes = open(fname, O_WRONLY | O_APPEND | O_CREAT | O_EXCL);
  if (fdes < 0)
  {
    // try to open existing, don't create new file
    alreadyExists = true;
    fdes = open(fname, O_WRONLY | O_APPEND);
  }

  return fdes;
}