iRule to read dynamic file in /tmp/ location

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1

Hi All, I’ve been trying to figure out if there is a way for an iRule to read from a file located in the /tmp/ directory on itself (LTM). The reason for this is I have a script running as a cronjob on the LTM to generate a unique string that I want to be able to manipulate and use in this iRule.

So in summary, can an irule read from a location on the itself(LTM) and store it as a string?

Thanks!

2

Maybe someone can correct me if I’m wrong, but I’m pretty sure you can’t access the file system through an iRule.

As a possible way around that, you could set your cron job up to run a

tmsh

command to update a

data group

with your unique string. Then your iRule could read the string from the data group (I don’t believe you can update a data group record within an iRule though).

Hope this helps.

3

Unfortunately, not possible at this point. TMOS and the underlying RHEL are kept separated on purpose. You can circumvent that since v11.4 (iCall). iRule calls the iCall → iCall calls the TCL script → TCL script interacts with the file in /tmp/ location. Can be a bit complicated if it’s your first time doing a workaround like this, suggest to decomission your idea :slight_smile:

4

Tried to update my original answer, but it wouldn’t save, so here’s the idea.

You can use the following commands to work with data groups from the command line:

CREATE
tmsh create / ltm data-group internal TEST_DATA_GROUP records add { MyKey { data MyValue } } type string

 MODIFY
tmsh modify / ltm data-group internal TEST_DATA_GROUP records replace-all-with { MyKey2 { data MyValue2 } }

 LIST
tmsh list / ltm data-group internal TEST_DATA_GROUP

In your iRule, you could grab the value like this

set myval [class match -value "MyKey" equals TEST_DATA_GROUP]