Sed from fish to bash

Question

I have a providers.tf containing content like:

provider "aws" {
  region = "${var.region}"

  assume_role {
    role_arn = "${var.role_arn}"
  }
}

I need to replace the region as well as the role_arn dynamically.

With fish, the following expression works fine

REGION="eu-central-1"
ROLE_ARN="arn:iam:mnsasa:asssasa/codebuild"
sed -i "s/region = \"${var.region}\"/region = \"${REGION}\"/g" providers.tf
sed -i "s/role_arn = \"${var.role_arn}\"/role_arn = \"${ROLE_ARN}\"/g" providers.tf

However, in bash, I got the following error

s/region = "${var.region}"/region = "${REGION}"/g: bad substitution

Which I guess is due to character not being correctly escaped in /bin/bash. So I went with escaping { and $

sed -i "s/region = \"\$\{var.region\}\"/region = \"${REGION}\"/g" providers.tf

Which gives me

sed -i 's/region = "$\{var.region\}"/region = "eu-central-1"/g' providers.tf
sed: -e expression #1, char 54: Invalid content of \{\}

Am I still missing some escaping here?

Ps - For Terraform people, I can't use variables here, because this is a pre-step of a terraform import commands which does not accept dynamic providers.

Answer 1

You can use

sed -i 's~\(region = "\)\${var\.region}"~\1'"$REGION"'"~g; s~\(role_arn = "\)\${var\.role_arn}"~\1'"$ROLE_ARN"'"~g' providers.tf

See an online demo:

#!/bin/bash
s='provider "aws" {
  region = "${var.region}"

  assume_role {
    role_arn = "${var.role_arn}"
  }
}'
REGION="eu-central-1"
ROLE_ARN="arn:iam:mnsasa:asssasa/codebuild"
sed 's~\(region = "\)\${var\.region}"~\1'"$REGION"'"~g; s~\(role_arn = "\)\${var\.role_arn}"~\1'"$ROLE_ARN"'"~g' <<< "$s"

Output:

provider "aws" {
  region = "eu-central-1"

  assume_role {
    role_arn = "arn:iam:mnsasa:asssasa/codebuild"
  }
}

In both commands, the part before a variable is quoted with single quotation marks, the variable is quoted with double quotation marks, and the rest is single-quote quoted.