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goproc

Apply Go templates to JSON or YAML data.

Install

go install github.com/dolmen-go/goproc@latest

Usage

goproc [ -env | -env=true | -env=VAR ] -e <Go-template-text> [ <JSON-or-YAML-file> ]
goproc [ -env | -env=true | -env=VAR ] -i <Go-template-file> [ <JSON-or-YAML-file> ]

The default input is STDIN in JSON format. Use -yaml flag to handle STDIN as YAML.

When an input file is given, the file extension determines if it is parsed as JSON or YAML.

In any case there is no magic detection (that usually lead to security issues).

Template syntax

See the Go templates documentation.

The Hugo documentation on Go templates may also be useful for a friendlier approach, but note that it contains references to features unique to Hugo (ex: partial).

Functions extensions

The following functions are available in addition to the standard functions.

env

Allow to use environment variables, with security protections.

This function must be explicitely enabled using the -env flag:

  • -env: enables the env function. Any environment variable can be used, but listing variables is blocked.
  • -env=: enables the env function, but whitelist of allowed variables is cleared (no variables allowed).
  • -env=name1,name2: enables the env function. Only the variables name1 and name2 are visible in calls to env.

Usage:

{{ env "HOME" }}     {{- /* Get value of HOME environment variable */}}
{{ "HOME" | env }}   {{- /* Get value of HOME environment variable */}}
{{ range $name, $value := env "HOME" "LANG" -}}
  {{ $name }}={{ $value }}
{{ end }}

error

Usage:

{{ error "message" }}

Example:

echo 0 | goproc -e '{{ error "fail!" }}'
template: :1:3: executing "" at <error "fail!">: error calling error: fail!

jsonptr

To ease the extraction of data, jsonptr allows to express data location using JSON Pointer (RFC 6901).

Usages:

{{ jsonptr "pointer" . }}
{{ . | jsonptr "pointer" }}

Examples:

  1. goproc testdata/02.gotmpl testdata/02.json
  2. goproc testdata/03.gotmpl testdata/03.json

json

Convert input to JSON.

Usage:

{{ json }}

Example:

echo '{"data": ["x"]}' | goproc -e '{{.data | json}}{{print "\n"}}'
["x"]

yaml

Convert input to YAML.

Usage:

{{ yaml }}

Example:

echo '{"data": ["x"]}' | goproc -e '{{.data | yaml}}'
- x

See also

https://github.com/naotookuda/go-template-cli

License

Copyright 2018-2024 Olivier Mengué

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.