multiple files define the same target, attributes are either merged or
overridden. In the case of overrides, the last one loaded takes precedence.

For example, given the following files:

```hcl {title=docker-bake.hcl}
variable "TAG" {
  default = "foo"
}

target "default" {
  tags = ["username/my-app:${TAG}"]
}
```

```hcl {title=docker-bake.override.hcl}
variable "TAG" {
  default = "bar"
}
```

Since `docker-bake.override.hcl` is loaded last in the default lookup order,
the `TAG` variable is overridden with the value `bar`.

```console
$ docker buildx bake --print
{
  "target": {
    "default": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "tags": ["username/my-app:bar"]
    }
  }
}
```

### Manual file overrides

You can use the `--file` flag to explicitly specify which files to load,
and use this as a way to conditionally apply override files.

For example, you can create a file that defines a set of configurations for a
specific environment, and load it only when building for that environment. The
following example shows how to load an `override.hcl` file that sets the `TAG`
variable to `bar`. The `TAG` variable is then used in the `default` target.

```hcl {title=docker-bake.hcl}
variable "TAG" {
  default = "foo"
}

target "default" {
  tags = ["username/my-app:${TAG}"]
}
```

```hcl {title=overrides.hcl}
variable "TAG" {
  default = "bar"
}
```

Printing the build configuration without the `--file` flag shows the `TAG`
variable is set to the default value `foo`.

```console
$ docker buildx bake --print
{
  "target": {
    "default": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "tags": [
        "username/my-app:foo"
      ]
    }
  }
}
```

Using the `--file` flag to load the `overrides.hcl` file overrides the `TAG`
variable with the value `bar`.

```console
$ docker buildx bake -f docker-bake.hcl -f overrides.hcl --print
{
  "target": {
    "default": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "tags": [
        "username/my-app:bar"
      ]
    }
  }
}
```

## Command line

You can also override target configurations from the command line with the
[`--set` flag](/reference/cli/docker/buildx/bake.md#set):

```hcl
# docker-bake.hcl
target "app" {
  args = {
    mybuildarg = "foo"
  }
}
```

```console
$ docker buildx bake --set app.args.mybuildarg=bar --set app.platform=linux/arm64 app --print
```

```json
{
  "group": {
    "default": {
      "targets": ["app"]
    }
  },
  "target": {
    "app": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "args": {
        "mybuildarg": "bar"
      },
      "platforms": ["linux/arm64"]
    }
  }
}
```

Pattern matching syntax defined in [https://golang.org/pkg/path/#Match](https://golang.org/pkg/path/#Match)
is also supported:

```console
$ docker buildx bake --set foo*.args.mybuildarg=value  # overrides build arg for all targets starting with "foo"