📜 Как использовать шаблоны внутри bash скриптов

Используйте шаблоны внутри shell скриптов, подставляя переменные среды.

Я буду использовать утилиту envsubst, которая является частью пакета gettext-base.

Создайте файл шаблона

Создайте шаблон, используя переменные среды.

$ cat configuration.yml

---
connection:
  database:
    name: ${DATABASE_NAME}
    type: ${DATABASE_TYPE}
  credentials:
    user: ${SATABASE_USER}
    pass: ${DATABASE_PASS}
  connection:
    host: ${DATABASE_HOST}
    port: ${DATABASE_PORT}

Простая подстановка переменных окружения

$ export DATABASE_NAME="bookmarks"
$ export DATABASE_TYPE="postgres"

$ export DATABASE_USER="book"
$ export DATABASE_PASS="worm"

$ export DATABASE_HOST="172.16.0.21"
$ export DATABASE_PORT="5432"

$ cat configuration.yml | envsubst 

---
connection:
  database:
    name: bookmarks
    type: postgres
  credentials:
    user: book
    pass: worm
  connection:
    host: 172.16.0.21
    port: 5432

$ export DATABASE_NAME="bookmarks"
$ export DATABASE_TYPE="postgres"

$ export DATABASE_USER="book"
$ export DATABASE_PASS="worm"

$ export DATABASE_HOST="172.16.0.22"
$ export DATABASE_PORT="5432"

$ envsubst < configuration.yml > bookmarks_connection.yml 

$ cat bookmarks_connection.yml 

---
connection:
  database:
    name: bookmarks
    type: postgres
  credentials:
    user: book
    pass: worm
  connection:
    host: 172.16.0.22

$ envsubst --variables '$DATABASE_USER $DATABASE_PASS $DATABASE_NAME $DATABASE_TYPE'

DATABASE_USER
DATABASE_PASS
DATABASE_NAME
DATABASE_TYPE

$ DATABASE_USER=book DATABASE_PASS=worm DATABASE_NAME=notes DATABASE_TYPE=postgres envsubst '$DATABASE_USER $DATABASE_PASS $DATABASE_NAME $DATABASE_TYPE' < configuration.yml > connection_temp.yml

$ cat connection_temp.yml 

---
connection:
  database:
    name: notes
    type: postgres
  credentials:
    user: book
    pass: worm
  connection:
    host: ${DATABASE_HOST}
    port: ${DATABASE_PORT}

$ envsubst --variables '$DATABASE_HOST $DATABASE_PORT'

DATABASE_HOST
DATABASE_PORT

$ DATABASE_HOST=localhost DATABASE_PORT=5432 envsubst '$DATABASE_HOST $DATABASE_PORT' < connection_temp.yml > connection_final.yml

$ cat connection_final.yml 

---
connection:
  database:
    name: notes
    type: postgres
  credentials:
    user: book
    pass: worm
  connection:
    host: localhost
    port: 5432

$ export DATABASE_NAME="files"
$ export DATABASE_TYPE="postgres"

$ export DATABASE_USER="book"
$ export DATABASE_PASS="worm"

$ export DATABASE_HOST="172.16.0.42"
$ export DATABASE_PORT="5432"

$ echo "${!DATABASE_@}"

DATABASE_HOST DATABASE_NAME DATABASE_PASS DATABASE_PORT DATABASE_TYPE DATABASE_USER

$ printf '${%s}\n' ${!DATABASE_@}

${DATABASE_HOST}
${DATABASE_NAME}
${DATABASE_PASS}
${DATABASE_PORT}
${DATABASE_TYPE}
${DATABASE_USER}

$ envsubst "$(printf '${%s}\n' ${!DATABASE_@})" < configuration.yml

---
connection:
  database:
    name: files
    type: postgres
  credentials:
    user: book
    pass: worm
  connection:
    host: 172.16.0.42
    port: 5432

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