reading from standard input instead of command line argument

[yukinying]

This would faciliate the use of pipe with terraform-validator. Consider the case for terraform show, this would remove the step of storing the intermediate artifacts on local disk.

[morgante]

Yes, this is a good idea. I'd say that if - is provided as the plan file name we should read from stdin.

terraform show -json ./terraform.tfplan | terraform-validator validate --policy-path=${POLICY_PATH} -