---
description: |
  Packer is controlled using a command-line interface. All interaction with
  Packer is done via the `packer` tool. Like many other command-line tools, the
  `packer` tool takes a subcommand to execute, and that subcommand may have
  additional options as well. Subcommands are executed with `packer SUBCOMMAND`,
  where "SUBCOMMAND" is the actual command you wish to execute.
layout: docs
page_title: Commands
sidebar_title: Commands (CLI)
---

# Packer Commands (CLI)

Packer is controlled using a command-line interface. All interaction with
Packer is done via the `packer` tool. Like many other command-line tools, the
`packer` tool takes a subcommand to execute, and that subcommand may have
additional options as well. Subcommands are executed with `packer SUBCOMMAND`,
where "SUBCOMMAND" is the actual command you wish to execute.

If you run `packer` by itself, help will be displayed showing all available
subcommands and a brief synopsis of what they do. In addition to this, you can
run any `packer` command with the `-h` flag to output more detailed help for a
specific subcommand.

In addition to the documentation available on the command-line, each command is
documented on this website. You can find the documentation for a specific
subcommand using the navigation to the left.

## Machine-Readable Output

By default, the output of Packer is very human-readable. It uses nice
formatting, spacing, and colors in order to make Packer a pleasure to use.
However, Packer was built with automation in mind. To that end, Packer supports
a fully machine-readable output setting, allowing you to use Packer in
automated environments.

Because the machine-readable output format was made with Unix tools in mind, it
is `awk`/`sed`/`grep`/etc. friendly and provides a familiar interface without
requiring you to learn a new format.

### Enabling Machine-Readable Output

The machine-readable output format can be enabled by passing the
`-machine-readable` flag to any Packer command. This immediately enables all
output to become machine-readable on stdout. Logging, if enabled, continues to
appear on stderr. An example of the output is shown below:

```shell-session
$ packer -machine-readable version
1498365963,,version,1.0.2
1498365963,,version-prelease,
1498365963,,version-commit,3ead2750b+CHANGES
1498365963,,ui,say,Packer v1.0.2
```

The format will be covered in more detail later. But as you can see, the output
immediately becomes machine-friendly. Try some other commands with the
`-machine-readable` flag to see!

~>; The `-machine-readable` flag is designed for automated environments and
is mutually-exclusive with the `-debug` flag, which is designed for interactive
environments.

### Format for Machine-Readable Output

The machine readable format is a line-oriented, comma-delimited text format.
This makes it more convenient to parse using standard Unix tools such as `awk`
or `grep` in addition to full programming languages like Ruby or Python.

The format is:

```text
timestamp,target,type,data...
```

Each component is explained below:

- `timestamp` is a Unix timestamp in UTC of when the message was printed.

- `target` When you call `packer build` this can be either empty or
  individual build names, e.g. `amazon-ebs`. It is normally empty when builds
  are in progress, and the build name when artifacts of particular builds are
  being referred to.

- `type` is the type of machine-readable message being outputted. The two
  most common `type`s are `ui` and `artifact`

- `data` is zero or more comma-separated values associated with the prior
  type. The exact amount and meaning of this data is type-dependent, so you
  must read the documentation associated with the type to understand fully.

Within the format, if data contains a comma, it is replaced with
`%!(PACKER_COMMA)`. This was preferred over an escape character such as `\'`
because it is more friendly to tools like `awk`.

Newlines within the format are replaced with their respective standard escape
sequence. Newlines become a literal `\n` within the output. Carriage returns
become a literal `\r`.

### Machine-Readable Message Types

Here's an incomplete list of types you may see in the machine-readable output:

You'll see these data types when you run `packer build`:

- `ui`: this means that the information being provided is a human-readable
  string that would be sent to stdout even if we aren't in machine-readable
  mode. There are three "data" subtypes associated with this type:

  - `say`: in a non-machine-readable format, this would be bolded. Normally
    it is used for anouncements about beginning new steps in the build
    process

  - `message`: the most commonly used message type, used for basic updates
    during the build process.

  - `error`: reserved for errors

- `artifact-count`: This data type tells you how many artifacts a particular
  build produced.

- `artifact`: This data type tells you information about what Packer created
  during its build. An example of output follows the pattern
  `timestamp, buildname, artifact, artifact_number, key, value` where `key`
  and `value` contain information about the artifact.

  For example:

  ```text
    1539967803,,ui,say,\n==> Builds finished. The artifacts of successful builds are:
    1539967803,amazon-ebs,artifact-count,2
    1539967803,amazon-ebs,artifact,0,builder-id,mitchellh.amazonebs
    1539967803,amazon-ebs,artifact,0,id,eu-west-1:ami-04d23aca8bdd36e30
    1539967803,amazon-ebs,artifact,0,string,AMIs were created:\neu-west-1: ami-04d23aca8bdd36e30\n
    1539967803,amazon-ebs,artifact,0,files-count,0
    1539967803,amazon-ebs,artifact,0,end
    1539967803,,ui,say,--> amazon-ebs: AMIs were created:\neu-west-1: ami-04d23aca8bdd36e30\n
    1539967803,amazon-ebs,artifact,1,builder-id,
    1539967803,amazon-ebs,artifact,1,id,
    1539967803,amazon-ebs,artifact,1,string,
    1539967803,amazon-ebs,artifact,1,files-count,0
    2018/10/19 09:50:03 waiting for all plugin processes to complete...
    1539967803,amazon-ebs,artifact,1,end
  ```

You'll see these data types when you run `packer version`:

- `version`: what version of Packer is running

- `version-prerelease`: Data will contain `dev` if version is prerelease, and
  otherwise will be blank.

- `version-commit`: The git hash for the commit that the branch of Packer is
  currently on; most useful for Packer developers.

## Autocompletion

The `packer` command features opt-in subcommand autocompletion that you can
enable for your shell with `packer -autocomplete-install`. After doing so, you
can invoke a new shell and use the feature.

For example, assume a tab is typed at the end of each prompt line:

```shell-session
$ packer p
plugin  build
$ packer build -
-color             -debug             -except            -force             -machine-readable  -on-error          -only              -parallel          -timestamp          -var               -var-file
```
