it-infra

MyRTR#show run ?

 brief       configuration without certificate data
 class-map   Show class-map information
 full        full configuration
 interface   Show interface configuration
 linenum     Display line numbers in output
 map-class   Show map class information
 policy-map  Show policy-map information
 view        View options
 |           Output modifiers
 <cr>

The option we are interested in is the “|” (Output modifier). We can quickly see that if we include that “|” as a parameter and use our trusty old “?”, we have more options.

MyRTR#show run | ?
 append    Append redirected output to URL (URLs supporting append operation
 only)
 begin     Begin with the line that matches
 exclude   Exclude lines that match
 include   Include lines that match
 redirect  Redirect output to URL
 section   Filter a section of output
 tee       Copy output to URL

The ones I find really useful are include, begin and section.  You can also play around with the exclude option as well.  I’ve not seen any real world use cases for the rest (but I’m sure they exist).  The simplest of these to understand is the “include” command.  This command parses the output of whatever command precedes the “|” and only presents whatever matches a filter that we need to provide.  For example, I could issue the command “show run | include address”.  The entire output of the running-config would be piped out to the include command and filtered against “address”.  So I would expect to see output similar to the following.

MyRTR#show run | inc address

 ip address 1.1.1.1 255.255.255.0
 ip address 2.2.2.2 255.255.255.0
 ip address 10.1.1.1 255.255.255.0

I could also get fancy with the filter that I am using.  I could use wildcards that are similar to regex.

//all instances of “address”
 MyRTR#show run | inc address
 ip address 1.1.1.1 255.255.255.0
 ip address 2.2.2.2 255.255.255.0
 ip address 10.1.1.1 255.255.255.0

//all instances of address with a space, a single character, then a period
 // the “.” In the filter is a wildcard and a “\.” matches a “.”–confusing
 MyRTR#show run | inc address .\.
 ip address 1.1.1.1 255.255.255.0
 ip address 2.2.2.2 255.255.255.0
 //notice we don’t see 10.1.1.1

The following characters have special meaning in regex and in the filter syntax.

 . (Period) Any Single Character : 임의의 단일문자
 * A multiplier that matches 0 or more sequences of the preceding character
 + A multiplier that matches 1 or more sequences of the preceding character
 ? A multiplier that matches 0 or 1 sequences of the preceding character
 ^ Matches the start of a line
 $ Matches the end of a line
 _ Matches Word Boundaries

If you need to match any of these characters, you must escape them in your filter by using a “\.”  To quickly see the effect of this issue the following two commands on a router.

MyRTR#show run | inc .
 Building configuration…
 Current configuration : 740 bytes
 !
 version 12.3
 service timestamps debug datetime msec
 service timestamps log datetime msec
 no service password-encryption
 !
 hostname MyRTR
 !
 boot-start-marker
 boot-end-marker
 !

< — Snip (it shows everything — >

MyRTR#show run | inc \.
 Building configuration…
 version 12.3
 ip address 1.1.1.1 255.255.255.0
 ip address 2.2.2.2 255.255.255.0
 ip address 10.1.1.1 255.255.255.0