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andreast_4666's avatar
andreast_4666
Icon for Nimbostratus rankNimbostratus
Oct 11, 2011

Universal Persistence

Hi,

 

 

I have been reading through the LTM Advance course book and have come up to universal persistence but am having trouble understanding an option in the example in the book:

 

 

when HTTP_REQUEST { persist uie [findstr [HTTP::uri] "user=" 5 "&"] }

 

 

Im trying to understand what the '5' in the persistence rule is?

 

 

they have a URI example of /env.cgi?user=123&pw456

 

 

Please any help would be much appreciated.

 

 

thanks in advance

 

Andreas
application delivery
dev
devops
iRules
  • hoolio's avatar
    hoolio
    Icon for Cirrostratus rankCirrostratus
    Oct 11, 2011
    Hi Andreas,

    You can read up on the details for findstr here:

    http://devcentral.f5.com/wiki/iRules.findstr.ashx

    Basically, findstr is looking in the URI for the string "user=" and then skipping five characters forward from the first character of user= and reading up to the end of the URI or to the next &. It's trying to parse the value of the "user" parameter.

    You could do this simpler using URI::query:

    
set user [URI::query [HTTP::uri] user]
if {$user ne ""}{
   persist uie $user
}

    If you're on v9 or v10, you can use a workaround for a bug in those versions:

    
set user [URI::query "?&[HTTP::query]" &user]
if {$user ne ""}{
   persist uie $user
}

    http://devcentral.f5.com/wiki/iRules.uri__query.ashx

    Aaron