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Forum Discussion

jojo83_271212's avatar
jojo83_271212
Icon for Nimbostratus rankNimbostratus
Oct 29, 2017

create irule with variable in iApp

Hi Devcentral! I've a questions: I'm modifying an iApp in order to create an irule to assign to the vs. the assignment is here { [iapp_conf create ltm virtual ${app}_vs \ destination [iapp_des...
application delivery
iApps
iRules
crodriguez's avatar
crodriguez
Ret. Employee
Oct 31, 2017

iApps are fussy with brackets, braces, and quotes, and need a lot of escape characters, especially when creating an iRule. As a result, I like to set a variable to the iRule code string (with all the escape characters) and then refer to the variable on the tmsh::create command, rather than try to do it all on one command. Makes maintenance a bit easier, too:

 

set MyRule "
when HTTP_REQUEST \{
   if \{ \[HTTP::uri\] starts_with \"/portal${app}_pool\" \} \{
      pool ${app}_pool
   \} else \{
      TCP::close
   \}
\}"
tmsh::create "/ltm rule ${app}_MyRule $MyRule"

Notice the braces in ${app} are not escaped so that the iApp processor will perform variable substitution when the application service is deployed. But all the braces, brackets, and quotes that need to be present in the finished iRule must be escaped.