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Jim_Araujo_1061's avatar
Jim_Araujo_1061
Icon for Nimbostratus rankNimbostratus
Jun 10, 2015

iRule to read dynamic file in /tmp/ location

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!

 

application delivery
batch file
BIG-IP Access Policy Manager (APM)
devops
file
iRules
security
string

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  • Michael_Jenkins's avatar
    Michael_Jenkins
    Icon for Cirrostratus rankCirrostratus
    Jun 10, 2015

    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.

  • Hannes_Rapp's avatar
    Hannes_Rapp
    Icon for Nimbostratus rankNimbostratus
    Jun 10, 2015

    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 :)

     

  • Michael_Jenkins's avatar
    Michael_Jenkins
    Icon for Cirrostratus rankCirrostratus
    Jun 11, 2015

    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]