如何在 Dockerfile CMD 中使用变量? [英] How can I use a variable inside a Dockerfile CMD?
问题描述
在我的 Dockerfile 中:
Inside my Dockerfile:
ENV PROJECTNAME mytestwebsite
CMD ["django-admin", "startproject", "$PROJECTNAME"]
错误:
CommandError: '$PROJECTNAME' is not a valid project name
这里最快的解决方法是什么?Docker 有没有计划在以后的 Docker 版本中修复"或引入这个功能?
What is the quickest workaround here? Does Docker have any plan to "fix" or introduce this functionality in later versions of Docker?
注意:如果我从 Docker 文件中删除 CMD 行，然后运行 Docker 容器，我可以从容器内部手动运行 Django-admin startproject $PROJECTNAME，它将创建项目...
NOTE: If I remove the CMD line from the Docker file and then run the Docker container, I am able to manually run Django-admin startproject $PROJECTNAME from inside the container and it will create the project...
推荐答案
当您使用执行列表时，例如...
When you use an execution list, as in...
CMD ["django-admin", "startproject", "$PROJECTNAME"]
...然后 Docker 将直接执行给定的命令，而不涉及 shell.由于不涉及外壳，这意味着:
...then Docker will execute the given command directly, without involving a shell. Since there is no shell involved, that means:
- 无变量扩展
- 无通配符扩展
- 没有使用
>、<、|等进行 I/O 重定向 - 没有通过
command1 的多个命令；命令2 - 等等.
- No variable expansion
- No wildcard expansion
- No i/o redirection with
>,<,|, etc - No multiple commands via
command1; command2 - And so forth.
如果你想让你的CMD扩展变量，你需要安排一个shell.你可以这样做:
If you want your CMD to expand variables, you need to arrange for a shell. You can do that like this:
CMD ["sh", "-c", "django-admin startproject $PROJECTNAME"]
或者你可以使用一个简单的字符串而不是一个执行列表，这样你得到的结果与前面的例子基本相同:
Or you can use a simple string instead of an execution list, which gets you a result largely identical to the previous example:
CMD django-admin startproject $PROJECTNAME
这篇关于如何在 Dockerfile CMD 中使用变量?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
