github.com/askholme/packer@v0.7.2-0.20140924152349-70d9566a6852/website/source/docs/templates/configuration-templates.html.markdown (about)

     1  ---
     2  layout: "docs"
     3  page_title: "Configuration Templates"
     4  ---
     5  
     6  # Configuration Templates
     7  
     8  All strings within templates are processed by a common Packer templating
     9  engine, where variables and functions can be used to modify the value of
    10  a configuration parameter at runtime.
    11  
    12  For example, the `{{timestamp}}` function can be used in any string to
    13  generate the current timestamp. This is useful for configurations that require
    14  unique keys, such as AMI names. By setting the AMI name to something like
    15  `My Packer AMI {{timestamp}}`, the AMI name will be unique down to the second.
    16  
    17  In addition to globally available functions like timestamp shown before,
    18  some configurations have special local variables that are available only
    19  for that configuration. These are recognizable because they're prefixed by
    20  a period, such as `{{.Name}}`.
    21  
    22  The complete syntax is covered in the next section, followed by a reference
    23  of globally available functions.
    24  
    25  ## Syntax
    26  
    27  The syntax of templates is extremely simple. Anything template related
    28  happens within double-braces: `{{ }}`. Variables are prefixed with a period
    29  and capitalized, such as `{{.Variable}}` and functions are just directly
    30  within the braces, such as `{{timestamp}}`.
    31  
    32  Here is an example from the VMware VMX template that shows configuration
    33  templates in action:
    34  
    35  <pre>
    36  .encoding = "UTF-8"
    37  displayName = "{{ .Name }}"
    38  guestOS = "{{ .GuestOS }}"
    39  </pre>
    40  
    41  In this case, the "Name" and "GuestOS" variables will be replaced, potentially
    42  resulting in a VMX that looks like this:
    43  
    44  <pre>
    45  .encoding = "UTF-8"
    46  displayName = "packer"
    47  guestOS = "otherlinux"
    48  </pre>
    49  
    50  ## Global Functions
    51  
    52  While some configuration settings have local variables specific to only that
    53  configuration, a set of functions are available globally for use in _any string_
    54  in Packer templates. These are listed below for reference.
    55  
    56  * `lower` - Lowercases the string.
    57  * `pwd` - The working directory while executing Packer.
    58  * `isotime [FORMAT]` - UTC time, which can be [formatted](http://golang.org/pkg/time/#example_Time_Format).
    59     See more examples below.
    60  * `timestamp` - The current Unix timestamp in UTC.
    61  * `uuid` - Returns a random UUID.
    62  * `upper` - Uppercases the string.
    63  
    64  ### isotime Format
    65  
    66  Formatting for the function `isotime` uses the magic reference date
    67  **Mon Jan 2 15:04:05 -0700 MST 2006**, which breaks down to the following:
    68  
    69   <table border="1" cellpadding="5" width="100%">
    70   	<tr bgcolor="lightgray">
    71   		<td></td>
    72   		<td align="center"><strong>Day of Week</strong></td>
    73   		<td align="center"><strong>Month</strong></td>
    74   		<td align="center"><strong>Date</strong></td>
    75   		<td align="center"><strong>Hour</strong></td>
    76   		<td align="center"><strong>Minute</strong></td>
    77   		<td align="center"><strong>Second</strong></td>
    78   		<td align="center"><strong>Year</strong></td>
    79   		<td align="center"><strong>Timezone</strong></td>
    80   	</tr>
    81   	<tr>
    82   		<td><strong>Numeric</strong></td>
    83   		<td align="center">-</td>
    84   		<td align="center">01</td>
    85   		<td align="center">02</td>
    86   		<td align="center">03 (15)</td>
    87   		<td align="center">04</td>
    88   		<td align="center">05</td>
    89   		<td align="center">06</td>
    90   		<td align="center">-0700</td>
    91   	</tr>
    92   	<tr>
    93   		<td><strong>Textual</strong></td>
    94   		<td align="center">Monday (Mon)</td>
    95   		<td align="center">January (Jan)</td>
    96   		<td align="center">-</td>
    97   		<td align="center">-</td>
    98   		<td align="center">-</td>
    99   		<td align="center">-</td>
   100   		<td align="center">-</td>
   101   		<td align="center">MST</td>
   102   	</tr>
   103   </table>
   104  
   105   _The values in parentheses are the abbreviated, or 24-hour clock values_
   106  
   107   Here are some example formated time, using the above format options:
   108  
   109   <pre>
   110  isotime = June 7, 7:22:43pm 2014
   111  
   112  {{isotime "2006-01-02"}} = 2014-06-07
   113  {{isotime "Mon 1506"}} = Sat 1914
   114  {{isotime "01-Jan-06 03\_04\_05"}} = 07-Jun-2014 07\_22\_43
   115  {{isotime "Hour15Year200603"}} = Hour19Year201407
   116  </pre>
   117  
   118  ## Amazon Specific Functions
   119  
   120  Specific to Amazon builders:
   121  
   122  * ``clean_ami_name`` - AMI names can only contain certain characters. This
   123    function will replace illegal characters with a '-" character. Example usage
   124    since ":" is not a legal AMI name is: `{{isotime | clean_ami_name}}`.