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The IOS and Its User Interface 31
*
When you type the ?, the IOS's CLI reacts immediately; that is, you don't need to press the Enter key or any
other keys. The router also redisplays what you typed before the ? to save you some keystrokes. If you press Enter
immediately after the ?, the IOS tries to execute the command with only the parameters you have typed so far.
**
"Command" represents any command, not the word "command." Likewise, "parm" represents a command's
parameter, not the word "parameter."
The context in which help is requested is also important. For example, when ? is typed in user
mode, the commands allowed only in privileged EXEC mode are not displayed. Also, help is
available in configuration mode; only configuration commands are displayed in that mode of
operation.
Commands you use at the CLI are stored in a command history buffer that retains the last
10 commands you typed. You can change the history size with the terminal history size x
command, where x is the number of commands for the CLI to recall; this can be set to a value
between 0 and 256.
Of course, most people want to use a previously typed command (perhaps with a different
parameter). Commands you have previously used during the current console/aux/Telnet can be
retrieved and then edited to save you some time and effort. This is particularly useful when you
are typing long configuration commands. Table 2-5 lists the commands used to manipulate
previously typed commands.
command parm<Tab>
If the user presses the Tab key midword, the CLI will either spell the rest
of this parameter at the command line for the user, or do nothing. If the
CLI does nothing, it means that this string of characters represents more
than one possible next parameter, so the CLI does not know which to
spell out.
command parm1 ?
If a space is inserted before the question mark, the CLI lists all next
parameters and gives a brief explanation of each.
Table 2-5
Key Sequences for Command Edit and Recall
Keyboard Command
What the User Gets
Up-arrow or Ctrl+p
This displays the most recently used command. If pressed again, the
next most recent command appears, until the history buffer is
exhausted. (The p stands for previous.)
Down-arrow or Ctrl+n
If you have gone too far back into the history buffer, these keys will go
forward, in order, to the more recently typed commands. (The n is for
next.)
Left-arrow or Ctrl+b
This moves the cursor backward in the currently displayed command
without deleting characters. (The b stands for back.)
Table 2-4
IOS Command Help (Continued)
What You Type
The Help You Get
continues
ch02.fm Page 31 Monday, March 20, 2000 4:57 PM