# Gateway Event Script - Tag Value Change

**URL:** <https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475>\
**Category:** Ignition\
**Tags:** scripting\
**Created:** [June 23, 2023, 7:32pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475 "2023-06-23T19:32:47Z")\
**Posts on this page:** 20\
**Page:** 1

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 23, 2023, 7:32pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/1 "2023-06-23T19:32:47Z")

</div>

The purpose of this script is to record the values of specific components as they were 5 seconds before an unintentional shut down. The script includes some conditions that must be met before writing to the CSV file. This is to ensure the script only writes when an unexpected shut down occurs, rather than a planned shutdown. Also, to make sure the script only writes once per shutdown event.

What the script should do is write to the CSV file one time per shutdown event. What the script is actually doing is writing to the CSV file every few minutes. This includes times when the first trigger component value is not zero. First of all, it shouldn't be writing very few minutes and second it should never write unless the value of the first trigger component is exactly zero.

Can anyone tell me where I've gone wrong with the code? If needed, I'm happy to provide more details for what I'm trying to achieve.

Thank you

Link to script: [GitHub - PeteGietl/Ignition-Pub at 04a3c2d1b8b1b99e00afb9f53c1711f8510197f4](https://github.com/PeteGietl/Ignition-Pub/tree/04a3c2d1b8b1b99e00afb9f53c1711f8510197f4)

I should also add that this script is being used in Ignition 7.9 (Jython). Upgrading is unfortunately not likely to happen and it's out of my control.

I've also replaced potentially sensitive data with an 'x'.

---

<div class="post-metadata">

**Author:** ![Transistor](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/transistor/32/3380_2.png) [@Transistor](https://forum.inductiveautomation.com/u/Transistor)\
**Post date:** [June 23, 2023, 7:52pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/3 "2023-06-23T19:52:46Z")

</div>

Tip: You can post the code here using the \</\> formatting button and, if you want, use the gear-icon, Hide Details option to collapse the selected code.

> **Code in here**
>
> ```auto
> for i in range(10):
> print("Syntax highlighting and preserved indentation.")
> 
> ```

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 23, 2023, 7:55pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/4 "2023-06-23T19:55:27Z")

</div>

Got it, thanks. Here's the code:

> **Gateway Event Script**
>
> ```auto
> import system
> import csv
> import time
> 
> # Define the list of triggering components
> triggerComponentPath = [
> {"path": "x/GVBED1/F19/F19:35"},
> {"path": "x/GVBED1/F53/F53:245"},
> ]
> 
> # Define the list of components to monitor with corresponding column headers
> componentPaths = [
> {"path": "x/GVBED1/F53/F53:60", "header": "D1 inlet temp"},
> {"path": "x/GVBED1/F53/F53:65", "header": "D1 outlet temp"},
> {"path": "x/GVBED1/F53/F53:70", "header": "D2 inlet temp"},
> {"path": "x/GVBED1/F53/F53:75", "header": "D2 outlet temp"},
> {"path": "x/GVBED1/F53/F53:80", "header": "D3 inlet temp"},
> {"path": "x/GVBED1/F53/F53:85", "header": "D3 outlet temp"},
> {"path": "x/GVBED1/F53/F53:115", "header": "Burn Chamber temp"},
> {"path": "x/GVBED1/F53/F53:120", "header": "Plenum temp"},
> {"path": "x/GVBED1/PD90/F554/F554:14", "header": "TCV-101 D1 Damper pos"},
> {"path": "x/GVBED1/N:108/TCV102", "header": "TCV-102 D2 Damper pos"},
> {"path": "x/GVBED1/PD90/F554/F554:16", "header": "TCV-103 D3 Damper pos"},
> {"path": "x/GVBED4/B10_Damper_Scaled_pos_Ing", "header": "B10 Damper pos"},
> {"path": "x/GVBED3/ACO_D4_Dry_Scaled", "header": "ACO moisture %"},
> {"path": "x/GVBED1/N110/TCV104", "header": "TCV-104 D3 Cold Damper pos"},
> {"path": "x/GVBED4/TCV107", "header": "TCV-107 D1 Cold Damper pos"},
> {"path": "x/GVBED4/TCV108", "header": "TCV-108 D2 Cold Damper pos"},
> {"path": "x/GVBED3/M15_Press_Fiber_Lbs_Hour", "header": "Lbs per hour"},
> {"path": "x/GVBED4/TE_Tank_Farm", "header": "Outside Temp"}
> ]
> 
> # Define the path of the CSV file to store the state information
> csvDirectoryPath = "C:\\Users\\x\\Documents\\Ignition Fire Report\\"
> csvFilePath = csvDirectoryPath + "output.csv"
> 
> # Initialize a flag variable to False
> eventTriggered = False
> 
> # Initialize a variable to store the previous state of the triggering conditions
> previousState = False
> 
> while True:
> ## Get the current timestamp
> currentTimestamp = system.date.now()
> 
> # Calculate the timestamp 5 seconds before the current time
> captureStartTimestamp = system.date.addSeconds(currentTimestamp, -5)
> 
> # Read the current value of the triggering components
> triggerComponentValues = [system.tag.read(trigger["path"]).value for trigger in triggerComponentPath]
> 
> # Check if the values of both triggering components reach zero
> currentState = triggerComponentValues[0] == 0 and triggerComponentValues[1] <= 8
> 
> # Check if the state has changed from False to True
> if currentState and not previousState:
> print("Trigger Component Values:", triggerComponentValues)
> 
> # Open the file in append mode using the csv module
> csvfile = open(csvFilePath, mode='a')
> writer = csv.writer(csvfile)
> 
> # Check if the file is empty
> if csvfile.tell() == 0:
> # Write column headers if the file is empty
> columnHeaders = ["Timestamp"]
> columnHeaders.extend(component["header"] for component in componentPaths)
> writer.writerow(columnHeaders)
> 
> # Capture component states
> states = [system.tag.read(component["path"]).value for component in componentPaths]
> 
> # Write captured states to CSV file
> row = [captureStartTimestamp]
> row.extend(states)
> writer.writerow(row)
> 
> # Close the CSV file
> csvfile.close()
> 
> print("Data written to CSV at", captureStartTimestamp)
> 
> # Update the previousState variable
> previousState = currentState
> 
> # Sleep for a short duration before checking again
> time.sleep(5)
> 
> ```

---

<div class="post-metadata">

**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [June 23, 2023, 8:14pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/5 "2023-06-23T20:14:16Z")

</div>

You should not be setting up an infinite while loop in an event script (or, generally speaking, anywhere in scripting).

You should rely on the existing facilities (such as a timer script) and use tags or `system.util.globals` to manage state between executions. What you've written is prone to memory leaks and is consuming one of a limited thread pool indefinitely.

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 23, 2023, 8:39pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/6 "2023-06-23T20:39:42Z")

</div>

Thanks for the feedback. I understand your point about memory consumption/leaks. A timer won't be appropriate for what I'm trying to achieve, but I'll see what else I can do to manage the state between executions.

---

<div class="post-metadata">

**Author:** ![lrose](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/lrose/32/62724_2.png) [@lrose](https://forum.inductiveautomation.com/u/lrose)\
**Post date:** [June 23, 2023, 8:50pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/7 "2023-06-23T20:50:05Z")

</div>

> [@Peter\_Gietl](#):
>
> A timer won't be appropriate for what I'm trying to achieve

Why not?

```python
while True:

```

combined with

```auto
time.sleep(5)

```

Is for all intents and purposes a script that executes every 5 seconds (or near enough).

A Timer Script set to a Fixed Delay of 5000ms will execute it's script with a 5 second delay between each invocation.

Everything above the while loop can be safely moved to Top Level project variables, and everything inside of the loop can be executed in the script.

In fact I would say that if you replaced the `while True` with `def checkState():`, removed the `timer.sleep(5)` and put all of this in a project script and then called `checkState()` from a Timer Event you would get exactly the same execution as you are expecting now.

---

<div class="post-metadata">

**Author:** ![nminchin](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nminchin/32/6911_2.png) [@nminchin](https://forum.inductiveautomation.com/u/nminchin)\
**Post date:** [June 24, 2023, 9:32am UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/8 "2023-06-24T09:32:26Z")

</div>

Also, this part here is extremely inefficient:

```auto
triggerComponentValues = [system.tag.read(trigger["path"]).value for trigger in triggerComponentPath]

```

if you're back in v7, the use system.tag.readAll to read a list of tagPaths. Reading them 1-by-1 is very slow and inefficient.  
Eg

```auto
triggerComponentValues = [qval.value for qval in system.tag.readAll(trigger)] 

```

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 26, 2023, 3:41pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/9 "2023-06-26T15:41:17Z")

</div>

The intent is for the script to execute any time the conditions for the trigger components are met (i.e., when an event occurs that causes an unexpected shutdown). Producing output from the script at timed intervals would not provide the necessary data.

Thank you for your feedback.

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 26, 2023, 3:41pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/10 "2023-06-26T15:41:58Z")

</div>

I see, thank you.

---

<div class="post-metadata">

**Author:** ![lrose](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/lrose/32/62724_2.png) [@lrose](https://forum.inductiveautomation.com/u/lrose)\
**Post date:** [June 26, 2023, 4:56pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/11 "2023-06-26T16:56:10Z")

</div>

> [@Peter\_Gietl](#):
>
> Producing output from the script at timed intervals would not provide the necessary data.

Okay, but that isn't what the script you provided would do. Once triggered your script as written will run indefinitely with a 5 second interval between executions (until it is stopped by some outside force).

If you only want the script to execute once, then the `while True` needs to be removed as well as the `time.sleep()`.

---

<div class="post-metadata">

**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\
**Post date:** [June 26, 2023, 5:05pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/12 "2023-06-26T17:05:33Z")

</div>

> [@Peter\_Gietl](#):
>
> I understand your point about memory consumption/leaks.

Any time you have a long-running task in Jython, it effectively **becomes** a memory leak as soon as anyone edits and saves the project it comes from (or any of the projects from which it inherits), because the event infrastructure will likely start another one in parallel. Then that task might very well be duplicating the work it is designed for.

Two pretty simple indicators that you are screwing up:

- Unbounded loop (`while True:` and friends)

- Any form of `.sleep()`, including CPU-burning spin loops that check a condition.

Perspective has some tolerance for short `.sleep()` operations, entirely due to its unbounded thread pool. The rest of Ignition, not so much.

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 26, 2023, 6:21pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/13 "2023-06-26T18:21:55Z")

</div>

I understand, thank you. My current script is not using while loops or time.sleep.

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 26, 2023, 6:27pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/14 "2023-06-26T18:27:03Z")

</div>

I understand. My current script is not using unbounded loops or any form of .sleep(). Thanks for providing further detail on the effects of my previous choices.

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 30, 2023, 7:21pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/15 "2023-06-30T19:21:19Z")

</div>

I appreciate your feedback and I've applied your advice. I don't want to miss the forest for the trees though, as my script is still producing unexpected output. This is the core issue I'm seeking help with. I've gone through several iterations with the same results: The script writes to the CSV file every few minutes even while the values for 'triggerComponent[0]' and 'previousValue0' remain unchanged at a value of 0 for each. I've been watching the tag values live as the script runs.

**Ignition 7.9**

**The purpose of the script:**

- To write the states of specific components to a file when an unexpected shutdown occurs
- This shutdown is caused by a type of event that occurs on average about 5 times per week
- Only one new line should be written per each event

**What I expect the script to do:**

- When the value of 'triggerComponent[0]' changes, the script runs
- Then it checks if the value for 'previousValue0' (this is a memory tag) is greater than or equal to 10  
(this is to ensure the script writes only when the event occurs) & 'triggerComponentValue[1] is less  
than or equal to 1
- If both are true, the script writes to the CSV file

**What the script is doing:**

- Writing to the CSV file every few minutes while the values that it checks remain at 0

**Additional Information**

- The only print statement that shows up in the 'wrapper.log' is "Data written to CSV at..."
- In the 'Gateway Tag Change Scripts' interface, I originally used both 'triggerComponent' tags in the  
'Tag Path(s)' window. I now have only triggerComponent[0].
- I've replace potentially sensitive info with an 'x'

Here is the current script. I will update lines as necessary for efficiency, but I would love to work out the core functionality first.

Thank you

> **Gateway Tag Change Script**
>
> ```auto
> import system
> import csv
> import os
> 
> # Define the list of triggering components
> triggerComponentPath = [
> "x/GVBED1/F19/F19:35",
> "x/GVBED1/F53/F53:245",
> ]
> 
> # Define the list of components to monitor with corresponding column headers
> componentPaths = [
> {"path": "x/GVBED1/F53/F53:60", "header": "D1 inlet temp"},
> {"path": "x/GVBED1/F53/F53:65", "header": "D1 outlet temp"},
> {"path": "x/GVBED1/F53/F53:70", "header": "D2 inlet temp"},
> {"path": "x/GVBED1/F53/F53:75", "header": "D2 outlet temp"},
> {"path": "x/GVBED1/F53/F53:80", "header": "D3 inlet temp"},
> {"path": "x/GVBED1/F53/F53:85", "header": "D3 outlet temp"},
> {"path": "x/GVBED1/F53/F53:115", "header": "Burn Chamber temp"},
> {"path": "x/GVBED1/F53/F53:120", "header": "Plenum temp"},
> {"path": "x/GVBED1/PD90/F554/F554:14", "header": "TCV-101 D1 Damper pos"},
> {"path": "x/GVBED1/N:108/TCV102", "header": "TCV-102 D2 Damper pos"},
> {"path": "x/GVBED1/PD90/F554/F554:16", "header": "TCV-103 D3 Damper pos"},
> {"path": "x/GVBED4/B10_Damper_Scaled_pos_Ing", "header": "B10 Damper pos"},
> {"path": "x/GVBED3/ACO_D4_Dry_Scaled", "header": "ACO moisture %"},
> {"path": "x/GVBED1/N110/TCV104", "header": "TCV-104 D3 Cold Damper pos"},
> {"path": "x/GVBED4/TCV107", "header": "TCV-107 D1 Cold Damper pos"},
> {"path": "x/GVBED4/TCV108", "header": "TCV-108 D2 Cold Damper pos"},
> {"path": "x/GVBED3/M15_Press_Fiber_Lbs_Hour", "header": "Lbs per hour"},
> {"path": "x/GVBED4/TE_Tank_Farm", "header": "Outside Temp"}
> ]
> 
> # Define the path of the CSV file to store the state information
> csvDirectoryPath = "C:\\Users\\x\\Documents\\Ignition Fire Report\\"
> csvFilePath = csvDirectoryPath + "output.csv"
> 
> # Define the path of the Memory Tag to store the previous state of triggerComponentValues[0]
> previousValue0TagPath = "x/GVBED1/F19/F19:35_previous"
> 
> # Initialize fire event flag
> fire_event_detected = False
> 
> # Event handler for Gateway Tag Change Event
> def tagChangeEvent(event):
> global fire_event_detected # Declare the flag as global to modify it
> 
> # Check if the event is due to the initial subscription
> if not event.initialChange:
> # Print when the tagChangeEvent function is called
> print "tagChangeEvent called at", system.date.now()
> 
> # Check if the tag that changed is F19:35
> if event.getTagPath() == "x/GVBED1/F19/F19:35":
> # Read the current value of the triggering components
> triggerComponentValues = [system.tag.read(tagPath).value for tagPath in triggerComponentPath]
> 
> # Read the previous value from the Memory Tag
> previousValue0 = system.tag.read(previousValue0TagPath).value
> 
> # Print the values of F19:35 and F19:35_previous
> print "F19:35 value:", triggerComponentValues[0]
> print "F19:35_previous value:", previousValue0
> 
> # Check if the previous value of triggering component[0] was at least 10 and the current value of triggerComponent[1] is 1 or less
> if previousValue0 >= 10 and triggerComponentValues[1] <= 1:
> if not fire_event_detected:
> # Fire event detected, set flag
> fire_event_detected = True
> print "Fire event detected, setting flag to True"
>                     
> # Get the current timestamp
> currentTimestamp = system.date.now()
> 
> # Open the file in append mode using the csv module
> csvfile = open(csvFilePath, "a")
> writer = csv.writer(csvfile)
> 
> # Check if the file is empty
> if os.path.isfile(csvFilePath) and os.path.getsize(csvFilePath) == 0:
> # Write column headers if the file is empty
> columnHeaders = ["Timestamp"]
> columnHeaders.extend(component["header"] for component in componentPaths)
> writer.writerow(columnHeaders)
> 
> # Capture component states
> states = [system.tag.read(component["path"]).value for component in componentPaths]
> 
> # Write captured states to CSV file
> row = [currentTimestamp]
> row.extend(states)
> writer.writerow(row)
> 
> csvfile.close()
> 
> print "Data written to CSV at", currentTimestamp
> 
> elif fire_event_detected and not (previousValue0 >= 10 and triggerComponentValues[1] <= 1):
> # Conditions for a fire event no longer met, reset flag
> fire_event_detected = False
> print "Fire event conditions no longer met, resetting flag to False"
>             
> # Update the previous value in the Memory Tag
> system.tag.write(previousValue0TagPath, triggerComponentValues[0])
> 
> ```

---

<div class="post-metadata">

**Author:** ![lrose](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/lrose/32/62724_2.png) [@lrose](https://forum.inductiveautomation.com/u/lrose)\
**Post date:** [June 30, 2023, 8:33pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/16 "2023-06-30T20:33:21Z")

</div>

If this is the whole script you have within the Gateway Tag Change Events Script window, then you have scoped the majority of your logic within the function `tagChangeEvent()` but that function is never called in the script.

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 30, 2023, 9:07pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/17 "2023-06-30T21:07:51Z")

</div>

Are you referring to, in the context of Ignition's Gateway Tag Change Scripts, the function that gets automatically called when a tag change event occurs is named `tagChange(event)` , not `tagChangeEvent(event)`?

---

<div class="post-metadata">

**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 30, 2023, 9:30pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/18 "2023-06-30T21:30:44Z")

</div>

**Update**

Before my post 2 hours ago, I disabled this script in Designer. When I came back after 2 hours, I checked my CSV file and there were several new lines written for this duration. So, I restarted the gateway. Now, after re-enabling the script, and after about 30 minutes, there are no new lines. This is good, but I assume this means some iteration of my script was lingering.

Is it considered best practice to restart the gateway after saving changes in Designer (this is only an option during planned downtime or emergency)? Are lingering processes associated with 7.9? Is there some other reason that may cause processes to linger?

---

<div class="post-metadata">

**Author:** ![nminchin](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nminchin/32/6911_2.png) [@nminchin](https://forum.inductiveautomation.com/u/nminchin)\
**Post date:** [June 30, 2023, 9:40pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/19 "2023-06-30T21:40:24Z")

</div>

> [@Peter\_Gietl](#):
>
> `if not event.initialChange`

I don't believe gateway tag change scripts have an initial change. I've been checking if the event.previousValue is not None

You should check the logs for any errors running your script

> [@Peter\_Gietl](#):
>
> Is it considered best practice to restart the gateway after saving changes in Designer

Generally no. The script engine will restart whenever you save changes. Although I'm not sure if currently running threads are affected or not. If they aren't, then your "while true" script would have still kept running, hence why you were still seeing values being inserted. Only a gw restart would fix that

---

<div class="post-metadata">

**Author:** ![lrose](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/lrose/32/62724_2.png) [@lrose](https://forum.inductiveautomation.com/u/lrose)\
**Post date:** [June 30, 2023, 9:50pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/20 "2023-06-30T21:50:05Z")

</div>

> [@Peter\_Gietl](#):
>
> Are you referring to, in the context of Ignition's Gateway Tag Change Scripts,

No, I’m referring to the function that is defined in the script you provided.

Unless you call the function after it is defined, any code in that scope will not be executed.

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**Author:** ![Peter\_Gietl](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Peter\_Gietl](https://forum.inductiveautomation.com/u/Peter_Gietl)\
**Post date:** [June 30, 2023, 9:52pm UTC](https://forum.inductiveautomation.com/t/gateway-event-script-tag-value-change/75475/21 "2023-06-30T21:52:50Z")

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> I don't believe gateway tag change scripts have an initial change. I've been checking if the event.previousValue is not None

> You should check the logs for any errors running your script

I added this condition based on info from the 7.9 manual. it's in there for previous troubleshooting and probably isn't needed anymore:

> - **initialChange** - a variable that is a flag (0 or 1) which indicates whether or not the event is due to the initial subscription or not. This is useful as you can filter out the event that is the initial subscription, preventing a script from running when the values haven't actually changed.

As for the logs, there have been no errors.

> your "while true" script would have still kept running

I think you're probably right about that 😢

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