Docker-compose：迭代传递的环境变量

Question

如何遍历传递的环境变量（每个脚本）并将它们写入文件（tmpfs 卷）？

docker-compose stop app 
envs=(env "a=hello" "b=world" "c=test")
"${envs[@]}" docker-compose up -d app

不应将所有其他环境变量写入文件。

我的 docker-compose 文件是

---

version: '3.9'
services:
  myservice:
    image: alpine
    command: >
      sh -c "echo ${a} > /use_secrets/a.txt &&
             echo ${b} > /use_secrets/b.txt "
    # iterate over all passed envs and pass them to tmpfs
    volumes:
     - share_tmpfs_vol:/secrets
  myreceiver:
    image: application
    volumes:
     - share_tmpfs_vol:/use_secrets