I'm trying to add an environment variable to azure functions, there is the "local.settings.json", but it's only for local development, though the documentation doesn't give any clue as to how I can set settings in production.
Any documentation about environment variable only explains how to READ environment variables, but I wish to WRITE an environment variable...
If no such file option exists, is it possible to set environment variables using the AZ cli?
There are several options and it depends a bit how you are deploying your function to Azure.
az functionapp config appsettings set [--ids]
[--name]
[--resource-group]
[--settings]
[--slot]
[--slot-settings]
[--subscription]
Where the -settings argument contains space separated name=value pairs.
This publishes your function app including your local settings to the cloud:
func azure functionapp publish <FunctionAppName> --publish-local-settings
This publishes only your local settings to your function app in the cloud:
func azure functionapp publish <FunctionAppName> --publish-settings-only
See https://docs.microsoft.com/en-us/azure/azure-functions/functions-run-local#project-file-deployment
If you're using Azure DevOps with Release Pipelines the Azure Function App task is convenient to use:
Supply the settings as space separated -key value pairs in the appSettings parameter in the task.
As Matt described you could add/update using the Azure Portal as well via Configuration -> Application Settings but I recommend against that if you're doing automated deployments (which you should ;).
To add the equivalent settings into Azure you need to create the setting under Configuration:
There are some issues/inconsistencies with how settings work in Azure for Azure Functions, see this github issue for more info, for example if you're trying to use a connection string with GetEnvironmentVariable you actually need to put this in as a normal setting in Azure e.g.:
