gotmpl is a command-line interface (CLI) tool for template rendering. Whether you're working with templates from stdin, files, or web resources, gotmpl simplifies the process by allowing you to provide multiple data inputs through arguments, files, or URLs. The rendered output can be directed to stdout or saved into a specified file.

$ echo "Hello, {{.Name}}" | go run main.go -data '{"Name": "John"}'
Hello, John%     

Currently supported arguments can be listed as follow.

$ ./gotmpl --help
Usage: gotmpl [options] -tmpl {URL,Path} -out {Path}
Options:
  -data value
        Data to use {URL,Path,JSON}. Multiple allowed.
  -help
        Show this help message.
  -out string
        Render output {Path} or stdout.
  -tmpl string
        Template to use {URL,Path} or stdin.

This cli tool uses the go text template engine. A documentation for that is available here. In general, the tool can be used as follow:

1. provide a template
   • from a file like -tmpl /some/path/mail_template.txt
   • from a web resource like -tmpl https://some.url/mail_template (requires http or https prefix)
   • from std like echo "template" | ... (without -tmpl argument)
2. provide data (for multiple data source see note below)
   • from a JSON formatted file like -tmpl /some/path/user_a.json
   • from a JSON formatted web resource like -tmpl https://some.url/user_a (requires http or https prefix)
   • directly as JSON formatted string -tmpl '{...}' or -tmpl '[...]'
3. define the output
   • into a file like -out result.txt
   • stdout is used by default if -out not defined

NOTE: When using multiple data sources, they are placed in an array (keeping the order). For example the templates will look as follow multiple data sources:

echo "Name: {{(index . 0).Name}}, Age: {{(index . 1).Age}}" | ./gotmpl -data '{"Name": "Nina"}' -data '{"Age": 33}'
# OR
echo "Name: {{index . 0 \"Name\"}}, Age: {{index . 1 \"Age\"}}" | ./gotmpl -data '{"Name": "Nina"}' -data '{"Age": 33}'

With single data source:

echo "Name: {{.Name}}, Age: {{.Age}}" | ./gotmpl -data '{"Name": "Nina", "Age": 33}'