Templater

Templater is a cli tool that helps you to quickly and easily create files from templates, using go template.

How to use

1. Inline variables

# File using helm templating
cat <<'EOF'>file
---
{{- $name := "John" }}
class:
{{- range $i := until 11 }}
  {{$i}}: {{$name}}
{{- end }}
EOF

templater -i file

# This will be the output

File: out/file
---
class:
  0: John
  1: John
  2: John
  3: John
  4: John
  5: John
  6: John
  7: John
  8: John
  9: John
  10: John

2. Passing variables from external yaml, using helm style templating.

# Value file
cat <<'EOF'>values.yaml
school: Govt. Public School
EOF
# File using helm templating
cat <<'EOF'>file
---
{{- $name := "John" }}
class:
  school: {{ .Values.school }}
{{- range $i := until 11 }}
  {{$i}}: {{$name}}
{{- end }}
EOF

templater -i file -f values.yaml -o out/

# This will be the output

File: out/file
---
class:
  school: Govt. Public School
  0: John
  1: John
  2: John
  3: John
  4: John
  5: John
  6: John
  7: John
  8: John
  9: John
  10: John

3. Using stdin

# Value file
cat <<'EOF'>values.yaml
name: Rajesh
EOF

echo "hi: {{.Values.name}}" | templater -f values.yaml -i -

output:

hi: Rajesh

4. Using --set to override values (Helm-compatible)

# Basic dot notation
templater -i deployment.yaml -f values.yaml --set app.replicas=3 --set app.enabled=true

# Arrays
templater -i template.yaml --set 'hosts={host1,host2,host3}'

# Array indexes
templater -i template.yaml --set 'servers[0].port=8080' --set 'servers[0].host=localhost'

# Escaping commas and dots
templater -i template.yaml --set 'annotation=value\,with\,commas'
templater -i template.yaml --set 'nodeSelector.kubernetes\.io/role=master'

Priority order (highest to lowest):

1. --set flags
2. -f values files (last file takes precedence over earlier ones)

Magic Functions

__replace: true

When using multiple -f files, maps are deep merged by default. To replace a map entirely instead of merging, add __replace: true to it.

# defaults.yaml
class:
  name: rajesh
  grade: 10

# overrides.yaml
class:
  __replace: true
  name: suresh

templater -i template.yaml -f defaults.yaml -f overrides.yaml
# Result: class has only {name: suresh} -- grade is dropped

The __replace annotation only affects values from earlier -f files. If a later -f file provides the same key, it merges normally (or replaces again if it also has __replace: true). The __replace key is stripped before template execution and never appears in output.

Installation

1. HomeBrew

brew install rjshrjndrn/tap/templater

2. Binary

Download the latest binary from Release Page.

3. Using go get

go install github.com/rjshrjndrn/templater/v6@latest

4. Github Action

- name: Download templater
  run: |
    curl https://i.jpillora.com/rjshrjndrn/templater! | bash