render-template

This tools allows rendering Handlebars 3.0 templates, using as context data the current environment variables or a provided data file.

Basic usage

$> render-template --help
Usage:
render-template [OPTIONS] [template-file]
Application Options:
-f, --data-file=DATA_FILE Properties file containing the replacements for the template
Help Options:
-h, --help Show this help message
Arguments:
template-file: File containing the template to render. Its contents can be also passed through stdin

The tool supports rendering templates from a file or from stdin (for convenience).

The source data is taken from the environment variables or from a data file, with properties-file format (key=value, a line for each pair). When a variable is defined both as an environment variable and in the data file, the latter will take precedence.

Examples

Render data from template file with environment variables

# Create the template
$>echo'hello {{who}}'> template.tpl
# Render it without 'who' variable
$> render-template template.tpl
hello # Render it with 'who' variable defined
$> who=bitnami render-template template.tpl
hello bitnami

Render data from stdin with environment variables

$> log_file=/tmp/stout.log port=8080 pid_file=/tmp/my.pid render-template <<"EOF"# My servide log filelog_file "{{log_file}}"# HTTP portport {{port}}# My service pid filepid_file "{{pid_file}}"EOF

Outputs:

# My servide log file
log_file "/tmp/stout.log"
# HTTP port
port 8080
# My service pid file
pid_file "/tmp/my.pid"

Render data from stdin with data file

# write data file
$> cat > data.properties <<"EOF"log_file=/tmp/stout.logport=8080pid_file=/tmp/my.pid EOF
$> render-template --data-file ./data.properties <<"EOF"# My servide log filelog_file "{{log_file}}"# HTTP portport {{port}}# My service pid filepid_file "{{pid_file}}"EOF

Outputs:

# My servide log file
log_file "/tmp/stout.log"
# HTTP port
port 8080
# My service pid file
pid_file "/tmp/my.pid"

Overriding environment variables in data file

# Lets define some environment variables
$>export name=foo
$>export company=bar
$>export year=3000
# And write a template
$> cat > data.tpl <<"EOF"{{name}} works at {{company}}since {{year}}EOF# Rendering from the environment would yield
$> render-template data.tpl
foo works at bar
since 3000
# But we can override it from a data file, either partially, to get a mix:
$>echo"name=mike"> data.properties
$> render-template --data-file data.properties data.tpl
mike works at bar
since 3000
# Or completely:
$> cat > data.properties <<"EOF"name=mikecompany=Bitnamiyear=2010EOF
$> render-template --data-file data.properties data.tpl
mike works at Bitnami
since 2010

Using helpers

The tool supports all the standard handlebars helpers: https://handlebarsjs.com/builtin_helpers.html

$> render-template <<"EOF"  {{#if author}}{{firstName}} {{lastName}} {{else}}Unknown Author {{/if}}EOF# Which outputs
Unknown Author
$> author=me firsName=foo lastName=bar render-template <<"EOF"  {{#if author}}{{firstName}} {{lastName}} {{else}}Unknown Author {{/if}}EOF# Outputs:
foo bar

In addition, it includes a few custom helpers:

json_escape

The json_escape helper converts the provided value into a valid JSON string

$>export VALUE='this is "a string", with quotingand some line breaks'

Without the helper:

$> render-template <<<'VALUE={{VALUE}}'
VALUE=this is "a string", with quoting
and some line breaks

Using the helper:

$> render-template <<<'VALUE={{json_escape VALUE}}'
VALUE="this is \"a string\", with quoting\n\nand some line breaks"

quote

The quote helper Quotes a string

Without the helper:

$> ARG1="some arg" ARG2="some other \"arg\"" render-template <<"EOF"ARG1={{ARG1}} ARG2={{ARG2}}EOF
ARG1=some arg ARG2=some other "arg"

With the helper

ARG1="some arg" ARG2="some other \"arg\"" render-template <<"EOF"ARG1={{quote ARG1}} ARG2={{quote ARG2}}EOF
ARG1="some arg" ARG2="some other \"arg\""

or

This helper allows using the "or" logical operation over two values (a value will be true if not empty)

To render a block when either "firstName" or "lastName" values ar not empty:

$> cat > data.tpl <<"EOF" {{#if (or firstName lastName)}}{{firstName}} {{lastName}}{{else}}Unknown Author{{/if}}EOF
$>render-template data.tpl
Unknown Author
$> firstName=foo render-template data.tpl
foo
$> lastName=bar render-template data.tpl
bar
$> firstName=foo lastName=bar render-template data.tpl
foo bar

This helper can also be used to provide defaults for your template variables:

# No value provided, so we fallback to the second "or" argument
$> render-template <<<'VALUE={{or ENV_VALUE "default value"}}'
VALUE=default value
# ENV_VALUE is defined, so we take it
$> ENV_VALUE="customized value" render-template <<<'VALUE={{or ENV_VALUE "default value"}}'
VALUE=customized value