packer-cn/website/source/docs/command-line/machine-readable.html.md

---
description: |
    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.
layout: docs
page_title: 'Machine-Readable Output - Command-Line'
...

# 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.

The machine-readable output format is easy to use and read and was made with
Unix tools in mind, so it is awk/sed/grep/etc. friendly.

## Enabling

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
1376289459,,version,0.2.4
1376289459,,version-prerelease,
1376289459,,version-commit,eed6ece
1376289459,,ui,say,Packer v0.2.4.dev (eed6ece+CHANGES)
```

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!

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

## Format

The machine readable format is a line-oriented, comma-delimited text format.
This makes it extremely easy 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-seperated 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`.

## Message Types

The set of machine-readable message types can be found in the [machine-readable
format](/docs/machine-readable/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.