如何让Terraform templatefile忽略Bash默认变量？

问题说明 #

将Bash脚本作为Terraform的user data使用时，需要仅让Terraform替换指定的${redis_ip}和${app_lb_dns}变量，但templatefile函数会解析脚本内所有${}格式的内容，包括Bash自身的颜色变量（如${G}、${R}），导致报错提示缺少对应变量键。尝试\${}和$${}转义未生效，需解决该冲突。

原Bash脚本 #

#!/bin/bash

#Colors for terminal

#RED
R="\e[31m"

#GREEN
G="\e[32m"

#YELLOW
Y="\e[33m"

#NORMAL
N="\e[0m"

validation(){

    if [ $1 -eq 0 ];
    then 
        echo -e "${G}$2 is successful${N}"
    else 
        echo -e "${R}$2 has Failed${N}"
        exit 1;
    fi
}

echo -e "${Y}Configuring Cart Service${N}"

cart_config="/etc/systemd/system/cart.service"

cat << EOF >$cart_config

Environment=REDIS_HOST="${redis_ip}" #I want TF to only substitute these
Environment=CATALOGUE_HOST="${app_lb_dns}"

Environment=CATALOGUE_PORT=8082

EOF

validation $? "Configuring Cart Service"

错误信息 #

20: user_data = base64encode(templatefile("../userdata/cart.sh", { redis_ip = data.aws_ssm_parameter.redis_ip.value, app_lb_dns = data.aws_ssm_parameter.app_lb_dns.value }))
while calling templatefile(path, vars)
Invalid value for "vars" parameter: vars map does not contain key "G", referenced at ../userdata/cart.sh:16,21-22.

翻译：调用templatefile(path, vars)函数时出错："vars"参数无效，变量映射中不存在键"G"，该引用位于../userdata/cart.sh第16行21-22位置。

原Terraform代码 #

user_data = base64encode(templatefile("../userdata/cart.sh", { redis_ip = data.aws_ssm_parameter.redis_ip.value, app_lb_dns = data.aws_ssm_parameter.app_lb_dns.value }))

解决方案 #

方法1：转义脚本中Bash自有变量（推荐） #

将脚本中所有不需要Terraform解析的${xxx}替换为$${xxx}，Terraform会将$${xxx}解析为${xxx}输出给Bash，仅保留指定变量让Terraform替换。

修改后的Bash脚本：

#!/bin/bash

#Colors for terminal

#RED
R="\e[31m"

#GREEN
G="\e[32m"

#YELLOW
Y="\e[33m"

#NORMAL
N="\e[0m"

validation(){

    if [ $1 -eq 0 ];
    then 
        echo -e "$${G}$2 is successful$${N}"
    else 
        echo -e "$${R}$2 has Failed$${N}"
        exit 1;
    fi
}

echo -e "$${Y}Configuring Cart Service$${N}"

cart_config="/etc/systemd/system/cart.service"

cat << EOF >$cart_config

Environment=REDIS_HOST="${redis_ip}" #I want TF to only substitute these
Environment=CATALOGUE_HOST="${app_lb_dns}"

Environment=CATALOGUE_PORT=8082

EOF

validation $? "Configuring Cart Service"

方法2：手动替换指定变量 #

不使用templatefile，改用file读取脚本原始内容，再通过replace函数手动替换目标变量，避免Terraform解析所有${}：

user_data = base64encode(
  replace(
    file("../userdata/cart.sh"),
    [
      "/\\${redis_ip}/", data.aws_ssm_parameter.redis_ip.value,
      "/\\${app_lb_dns}/", data.aws_ssm_parameter.app_lb_dns.value
    ]
  )
)

内容的提问来源于stack exchange，提问作者N-CODER