cmd
— 支持面向行的命令解释器
¶
源代码： Lib/cmd.py
The
Cmd
类为编写面向行的命令解释器提供简单框架。这些对测试治具、管理工具及稍后将包裹在更完备界面中的原型，经常很有用。
cmd.
Cmd
(
[
completekey
[
,
stdin
[
,
stdout
]
]
]
)
¶
A
Cmd
实例 (或子类实例) 是面向行的解释器框架。没有很好的理由实例化
Cmd
自身；在一定程度上，它作为解释器类的超类很有用，可以自己定义为继承
Cmd
的方法和封装动作方法。
可选自变量
completekey
是
readline
名称为补全键；默认为
Tab
。若
completekey
不是
None
and
readline
可用，命令补全是自动完成的。
可选自变量
stdin
and
stdout
指定 Cmd 实例 (或子类实例) 将用于输入/输出的输入/输出文件对象。若未指定，它们默认为
sys.stdin
and
sys.stdout
.
若想要给定
stdin
待使用，确保设置实例的
use_rawinput
属性为
False
，否则
stdin
将被忽略。
Changed in version 2.3: The stdin and stdout 参数被添加。
A
Cmd
实例具有下列方法：
Cmd.
cmdloop
(
[
intro
]
)
¶
重复发出提示、接受输入、剖析收到输入的初始前缀，并将其分派给动作方法，将行剩余部分作为自变量传递给它们。
可选自变量是发出的横幅 (或介绍) 字符串在第一提示前 (这覆写
intro
类属性)。
若
readline
module is loaded, input will automatically inherit
bash
-like history-list editing (e.g.
Control-P
scrolls back to the last command,
Control-N
forward to the next one,
Control-F
moves the cursor to the right non-destructively,
Control-B
moves the cursor to the left non-destructively, etc.).
An end-of-file on input is passed back as the string
'EOF'
.
An interpreter instance will recognize a command name
foo
if and only if it has a method
do_foo()
. As a special case, a line beginning with the character
'?'
is dispatched to the method
do_help()
. As another special case, a line beginning with the character
'!'
is dispatched to the method
do_shell()
(if such a method is defined).
This method will return when the
postcmd()
method returns a true value. The
stop
自变量对于
postcmd()
is the return value from the command’s corresponding
do_*()
方法。
If completion is enabled, completing commands will be done automatically, and completing of commands args is done by calling
complete_foo()
采用自变量
text
,
line
,
begidx
，和
endidx
.
text
is the string prefix we are attempting to match: all returned matches must begin with it.
line
is the current input line with leading whitespace removed,
begidx
and
endidx
are the beginning and ending indexes of the prefix text, which could be used to provide different completion depending upon which position the argument is in.
All subclasses of
Cmd
inherit a predefined
do_help()
. This method, called with an argument
'bar'
, invokes the corresponding method
help_bar()
, and if that is not present, prints the docstring of
do_bar()
, if available. With no argument,
do_help()
lists all available help topics (that is, all commands with corresponding
help_*()
methods or commands that have docstrings), and also lists any undocumented commands.
Cmd.
onecmd
(
str
)
¶
Interpret the argument as though it had been typed in response to the prompt. This may be overridden, but should not normally need to be; see the
precmd()
and
postcmd()
methods for useful execution hooks. The return value is a flag indicating whether interpretation of commands by the interpreter should stop. If there is a
do_*()
method for the command
str
, the return value of that method is returned, otherwise the return value from the
default()
method is returned.
Cmd.
emptyline
(
)
¶
Method called when an empty line is entered in response to the prompt. If this method is not overridden, it repeats the last nonempty command entered.
Cmd.
default
(
line
)
¶
Method called on an input line when the command prefix is not recognized. If this method is not overridden, it prints an error message and returns.
Cmd.
completedefault
(
text
,
line
,
begidx
,
endidx
)
¶
Method called to complete an input line when no command-specific
complete_*()
method is available. By default, it returns an empty list.
Cmd.
precmd
(
line
)
¶
Hook method executed just before the command line
line
is interpreted, but after the input prompt is generated and issued. This method is a stub in
Cmd
; it exists to be overridden by subclasses. The return value is used as the command which will be executed by the
onecmd()
method; the
precmd()
implementation may re-write the command or simply return
line
不变。
Cmd.
postcmd
(
stop
,
line
)
¶
Hook method executed just after a command dispatch is finished. This method is a stub in
Cmd
; it exists to be overridden by subclasses.
line
is the command line which was executed, and
stop
is a flag which indicates whether execution will be terminated after the call to
postcmd()
; this will be the return value of the
onecmd()
method. The return value of this method will be used as the new value for the internal flag which corresponds to
stop
; returning false will cause interpretation to continue.
Cmd.
preloop
(
)
¶
Hook method executed once when
cmdloop()
is called. This method is a stub in
Cmd
; it exists to be overridden by subclasses.
Cmd.
postloop
(
)
¶
Hook method executed once when
cmdloop()
is about to return. This method is a stub in
Cmd
; it exists to be overridden by subclasses.
实例化的
Cmd
subclasses have some public instance variables:
Cmd.
prompt
¶
The prompt issued to solicit input.
Cmd.
identchars
¶
The string of characters accepted for the command prefix.
Cmd.
lastcmd
¶
The last nonempty command prefix seen.
Cmd.
cmdqueue
¶
A list of queued input lines. The cmdqueue list is checked in
cmdloop()
when new input is needed; if it is nonempty, its elements will be processed in order, as if entered at the prompt.
Cmd.
intro
¶
A string to issue as an intro or banner. May be overridden by giving the
cmdloop()
方法自变量。
Cmd.
doc_header
¶
The header to issue if the help output has a section for documented commands.
Cmd.
misc_header
¶
The header to issue if the help output has a section for miscellaneous help topics (that is, there are
help_*()
methods without corresponding
do_*()
方法)。
Cmd.
undoc_header
¶
The header to issue if the help output has a section for undocumented commands (that is, there are
do_*()
methods without corresponding
help_*()
方法)。
Cmd.
ruler
¶
The character used to draw separator lines under the help-message headers. If empty, no ruler line is drawn. It defaults to
'='
.
Cmd.
use_rawinput
¶
标志，默认为 True。若 True，
cmdloop()
使用
raw_input()
to display a prompt and read the next command; if false,
sys.stdout.write()
and
sys.stdin.readline()
are used. (This means that by importing
readline
, on systems that support it, the interpreter will automatically support
Emacs
-like line editing and command-history keystrokes.)