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Parameter and Variable

https://learn.microsoft.com/en-us/azure/devops/pipelines/security/inputs?view=azure-devops

Parameters

  • Pipeline parameters can't be changed by a pipeline while it's running.

  • Parameters have data types such as number and string, and they can be restricted to a subset of values.

  • The setup ensures that the pipeline won't take arbitrary data.

Variables

https://learn.microsoft.com/en-us/azure/devops/pipelines/process/variables?view=azure-devops&tabs=yaml%2Cbatch

In YAML pipelines, we can set variables at the root, stage, and job level.

  • Variables can be a convenient way to collect information from the user up front.

  • We can also use variables to pass data from step to step within a pipeline.

  • Newly created variables are read-write by default.

variables:
  a: ${{ variables.var }} #evaluated when the YAML file is compiled into a plan
  b: $(var)               #evaluated at runtime before a task executes
  b: $[variables.var]     #evaluated at runtime

  • compile-time expression ${{ <expression> }}: have access to parameters and statically defined variables

  • runtime expression $[ <expression> ]: have access to more variables but no parameters