packer-cn/website/source/docs/commands/index.html.md

---
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_current: 'docs-commands'
---

# 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:

``` text
$ 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` is the target of the following output. This is empty if the message
    is related to Packer globally. Otherwise, this is generally a build name so
    you can relate output to a specific build while parallel builds are running.

-   `type` is the type of machine-readable message being outputted. There are a
    set of standard types which are covered later, but each component of Packer
    (builders, provisioners, etc.) may output their own custom types as well,
    allowing the machine-readable output to be infinitely flexible.

-   `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

The set of machine-readable message types can be found in the
[machine-readable format](/docs/commands/index.html) complete
documentation section. This section contains documentation on all the message
types exposed by Packer core as well as all the components that ship with
Packer by default.