"netrc" --- netrc 文件处理
**************************

**源代码:** Lib/netrc.py

======================================================================

"netrc" 类解析并封装了 Unix 的 **ftp** 程序和其他 FTP 客户端所使用的
netrc 文件格式。

class netrc.netrc([file])

   "netrc" 的实例或其子类的实例会被用来封装来自 netrc 文件的数据。 如
   果有初始化参数，它将指明要解析的文件。 如果未给出参数，则位于用户家
   目录的 ".netrc" 文件 -- 即 "os.path.expanduser()" 所确定的文件 --
   将会被读取。 在其他情况下，则将引发 "FileNotFoundError" 异常。 解析
   错误将引发 "NetrcParseError" 并附带诊断信息，包括文件名、行号以及终
   止令牌。 如果在 POSIX 系统上未指明参数，则当 ".netrc" 文件中有密码
   时，如果文件归属或权限不安全（归属的用户不是运行进程的用户，或者可
   供任何其他用户读取或写入）将引发 "NetrcParseError"。 这实现了与 ftp
   和其他使用 ".netrc" 的程序同等的安全行为。

   在 3.4 版更改: 添加了 POSIX 权限检查。

   在 3.7 版更改: "os.path.expanduser()" is used to find the location
   of the ".netrc" file when *file* is not passed as argument.

exception netrc.NetrcParseError

   Exception raised by the "netrc" class when syntactical errors are
   encountered in source text.  Instances of this exception provide
   three interesting attributes:  "msg" is a textual explanation of
   the error, "filename" is the name of the source file, and "lineno"
   gives the line number on which the error was found.


netrc Objects
=============

A "netrc" instance has the following methods:

netrc.authenticators(host)

   Return a 3-tuple "(login, account, password)" of authenticators for
   *host*. If the netrc file did not contain an entry for the given
   host, return the tuple associated with the 'default' entry.  If
   neither matching host nor default entry is available, return
   "None".

netrc.__repr__()

   Dump the class data as a string in the format of a netrc file.
   (This discards comments and may reorder the entries.)

Instances of "netrc" have public instance variables:

netrc.hosts

   Dictionary mapping host names to "(login, account, password)"
   tuples.  The 'default' entry, if any, is represented as a pseudo-
   host by that name.

netrc.macros

   Dictionary mapping macro names to string lists.

注解:

  Passwords are limited to a subset of the ASCII character set.  All
  ASCII punctuation is allowed in passwords, however, note that
  whitespace and non-printable characters are not allowed in
  passwords.  This is a limitation of the way the .netrc file is
  parsed and may be removed in the future.
