EEM QA: what were they (not) doing?
When I was writing the applet that should stop accidental scheduled router reloads, I wanted to use the action string match command to perform pattern matching on the output of the show reload command. Somehow the applet didn’t want to work as expected, so I checked the documentation on Cisco’s web site.
Reading the command description, I should have realized the whole thing must be broken. It looks like the documentation writer was fast asleep; even someone with a major in classical philosophy and zero exposure to networking should be able to spot the glaring logical inconsistencies.
Judging by the quality of the documentation, I started wondering if someone mixed up the order of parameters, so I swapped the pattern and the string. No luck. Totally fed up, I spent 30 seconds cut-and-pasting together a short test case:
event manager applet CheckMatchCommand
action 1.0 string match "a" "a"
action 1.1 puts "match: -a- versus -a- result: $_string_result"
action 2.0 string match "aa" "a"
action 2.1 puts "match: -aa- versus -a- result: $_string_result"
action 3.0 string match "a" "aa"
action 3.1 puts "match: -a- versus -aa- result: $_string_result"
action 4.0 string match "a." "aa"
action 4.1 puts "match: -a.- versus -aa- result: $_string_result"
action 5.0 string match "aa" "a."
action 5.1 puts "match: -aa- versus -a.- result: $_string_result"
action 6.0 string match "." "a"
action 6.1 puts "match: -.- versus -a- result: $_string_result"
action 7.0 string match "a" "."
action 7.1 puts "match: -a- versus -.- result: $_string_result"
Here are the results:
EEM#show version | inc IOS Software
Cisco IOS Software, 7200 Software (C7200-ADVIPSERVICESK9-M), Version 15.0(1)M4
EEM#event man run CheckMatchCommand
match: -a- versus -a- result: 1
match: -aa- versus -a- result: 0
match: -a- versus -aa- result: 0
match: -a.- versus -aa- result: 0
match: -aa- versus -a.- result: 0
match: -.- versus -a- result: 0
match: -a- versus -.- result: 0
As you can see, the string match command has nothing to do with pattern matching. It’s a simple string comparison, returning 1 if the two strings are equal and 0 if they are not.
Faced with such a huge discrepancy between documentation and actual behavior, one is forced to ask: what was the QA team doing? Did anyone ever test this feature? And last but not least: does this mean that nobody is using EEM 3.0 features or writing EEM applets? EEM 3.0 is almost two years old; such an obvious bug should have been reported and fixed by now.
% string match "a*" "aba"
% string match "a*b?z" "aeb1z"
% string match "a*b?z" "aeb1zz"
Here is description:
string match pattern string
See if pattern matches string; return 1 if it does, 0 if it doesn't. Matching is done in a fashion similar to that used by the C-shell. For the two strings to match, their contents must be identical except that the following special sequences may appear in pattern:
Matches any sequence of characters in string, including a null string.
Matches any single character in string.
Matches any character in the set given by chars. If a sequence of the form x-y appears in chars, then any character between x and y, inclusive, will match.
Matches the single character x. This provides a way of avoiding the special interpretation of the characters *?\ in pattern.