How to parse “show flow monitor-map” output with Tcl

I’m the organizer of a few Meetups, most successful so far is the MySQL Meetup. However, I also started a Tcl Meetup and today, a new member, Maryam (or “Moryam”) joined and sent me a message asking a Tcl question. I decided to answer it on my blog, so others could see the answer.

Her question is: How can I parse the output of “show flow monitor-map” from Cisco IOS into a “keyed list” (or Tcl array)?

Here is what she sent me as sample input and desired sample output:

RP/0/RP1/CPU0:irace-netflow-r1#show flow monitor-map

Flow Monitor Map : fmm1
-------------------------------------------------
Id: 1
RecordMapName: ipv4-raw
ExportMapName: fem1
CacheAgingMode: Normal
CacheMaxEntries: 65535
CacheActiveTout: 1800 seconds
CacheInactiveTout: 15 seconds
CacheUpdateTout: N/A

flowMonitorMap {
    {identifier fmm1}
    {id 1}
    {recordMapName ipv4-raw}
    {exportMapName fem1}
    {cacheAgingMode Normal}
    { cacheMaxEntries 65535}
    {cacheActiveTout 1800}
    { cacheActiveToutUnit Seconds}
    {cacheInactiveTout 15}
    {cacheInactiveToutUnit Seconds}
    {cacheUpdateTout N/A}
}

I’m going to assume that all the network I/O required (probably using something like Expect to automate that task) has already been implemented. For the sake of the code example, I’m putting the output of the “show flow monitor-map” into the variable $input. The result of the parsing will go into a Tcl array, which is an unordered set of key-value pairs. Here is the code:

##
## Set input data.
##

set input {Flow Monitor Map : fmm1
-------------------------------------------------
Id: 1
RecordMapName: ipv4-raw
ExportMapName: fem1
CacheAgingMode: Normal
CacheMaxEntries: 65535
CacheActiveTout: 1800 seconds
CacheInactiveTout: 15 seconds
CacheUpdateTout: N/A}

##
## Initialize output array
##

array unset output
array set output {}

##
## Parse input data, populate output array.
##

foreach line [split $input "\n"] {
    if {[regexp {^([^:]+?)\s*:\s*(\S+)\s*(\S+)?$} $line -> key value units]} {
        if {$key eq "Flow Monitor Map"} {
            set key "identifier"
        }
        set key [string tolower $key 0 0]
        set output($key) $value
        if {[string length $units]} {
            set output(${key}Unit) $units
        }
    }
}

##
## Optional: Display the output.
##

foreach {key value} [array get output] {
    puts [list $key $value]
}

Running this Tcl script produces this output:

cacheActiveToutUnit seconds
cacheActiveTout 1800
cacheMaxEntries 65535
exportMapName fem1
id 1
recordMapName ipv4-raw
cacheUpdateTout N/A
cacheInactiveToutUnit seconds
cacheInactiveTout 15
cacheAgingMode Normal
identifier fmm1

Remember, Tcl arrays are unordered lists, which is why the key-value pairs printed come back in a different order than they were put in. If you need them ordered, you’ll have to specify the ordering, perhaps like this:

foreach key {identifier id recordMapName exportMapName cacheAgingMode
        cacheMaxEntries cacheActiveTout cacheActiveToutUnit
        cacheInactiveTout cacheInactiveToutUnit
        cacheUpdateTout cacheUpdateToutUnit} {
    if {[info exists output($key)]} {
        puts [list $key $output($key)]
    }
}

This will produce the following output:

identifier fmm1
id 1
recordMapName ipv4-raw
exportMapName fem1
cacheAgingMode Normal
cacheMaxEntries 65535
cacheActiveTout 1800
cacheActiveToutUnit seconds
cacheInactiveTout 15
cacheInactiveToutUnit seconds
cacheUpdateTout N/A

Maryam, I hope this helps answer your question, as well as anyone else who’s looking to accomplish a similar task. Have questions or comments about the code? Leave them in the comments section below!

Tags:
Tcl,
MySQL,
Meetup,
Cisco,
IOS,
NetFlow,
HOWTO