Helm Sprig print quote default Functions

💡 Quick Answer: `print` concatenates values without separators, `quote` wraps strings in double quotes for YAML safety, and `default` provides fallback values when a variable is empty or undefined. These three Sprig functions handle 90% of Helm string formatting needs.

The Problem

Helm templates generate YAML, and YAML is whitespace-sensitive and type-sensitive. Common issues include:

• Values with special characters breaking YAML parsing
• Undefined values causing template rendering failures
• Need to format strings without the spaces that `cat` inserts

flowchart LR
    INPUT["Template Value"] --> PRINT["print<br/>No separators"]
    INPUT --> QUOTE["quote<br/>YAML-safe strings"]
    INPUT --> DEFAULT["default<br/>Fallback values"]
    PRINT --> YAML["Valid YAML Output"]
    QUOTE --> YAML
    DEFAULT --> YAML

The Solution

The `print` Function

`print` concatenates values without spaces (unlike `cat` which adds spaces):

# cat vs print comparison
{{ cat "hello" "world" }}        # → "hello world" (space between)
{{ print "hello" "world" }}      # → "helloworld"  (no space)

# Build resource names
{{ print .Release.Name "-" .Chart.Name }}
# → "myrelease-mychart"

# Construct image references
image: {{ print .Values.image.registry "/" .Values.image.repository ":" .Values.image.tag }}
# → "registry.example.com/myapp:v1.2.3"

`printf` — Formatted Output

# printf uses Go fmt verbs
{{ printf "%s-%s" .Release.Name .Chart.Name }}
# → "myrelease-mychart"

# With numbers
{{ printf "port-%d" .Values.service.port }}
# → "port-8080"

# Padding
{{ printf "%-20s %s" .Values.name .Values.version }}
# → "myapp                v1.2.3"

# Common Kubernetes pattern: generate annotation values
annotations:
  app.kubernetes.io/version: {{ printf "%s+build.%s" .Chart.AppVersion .Values.buildId | quote }}

The `quote` Function

`quote` wraps a value in double quotes, escaping special characters:

# Basic quoting
{{ quote .Values.config.message }}
# Input: Hello "World"
# Output: "Hello \"World\""

# CRITICAL for annotations and labels with special chars
metadata:
  annotations:
    description: {{ .Values.description | quote }}
    # Without quote: description: My app: the best → YAML ERROR (colon)
    # With quote:    description: "My app: the best" → Valid YAML

  labels:
    version: {{ .Values.version | quote }}
    # Without quote: version: 1.0 → parsed as float
    # With quote:    version: "1.0" → kept as string

When to Quote

# Real-world: Prometheus annotations
metadata:
  annotations:
    prometheus.io/scrape: {{ .Values.metrics.enabled | quote }}
    prometheus.io/port: {{ .Values.metrics.port | quote }}
    prometheus.io/path: {{ .Values.metrics.path | quote }}

`squote` — Single Quotes

# squote uses single quotes instead of double
{{ squote .Values.password }}
# → 'mysecretpassword'

# Useful for shell commands in containers
command:
  - /bin/sh
  - -c
  - echo {{ squote .Values.message }}

The `default` Function

`default` returns a fallback value when the input is empty, nil, zero, or false:

# Basic usage
{{ default "nginx" .Values.image.repository }}
# If .Values.image.repository is set:   → its value
# If .Values.image.repository is empty:  → "nginx"

# Common Kubernetes patterns
image: {{ default "latest" .Values.image.tag }}
replicas: {{ default 1 .Values.replicas }}
namespace: {{ default .Release.Namespace .Values.namespace }}

What Triggers `default`

# Chain defaults with other functions
metadata:
  labels:
    app: {{ default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" | quote }}
    version: {{ default .Chart.AppVersion .Values.image.tag | quote }}

# Resource limits with defaults
resources:
  limits:
    cpu: {{ default "500m" .Values.resources.limits.cpu | quote }}
    memory: {{ default "256Mi" .Values.resources.limits.memory | quote }}
  requests:
    cpu: {{ default "200m" .Values.resources.requests.cpu | quote }}
    memory: {{ default "128Mi" .Values.resources.requests.memory | quote }}

Combining All Three

# Full deployment label block
metadata:
  name: {{ printf "%s-%s" .Release.Name (default .Chart.Name .Values.nameOverride) }}
  labels:
    app.kubernetes.io/name: {{ default .Chart.Name .Values.nameOverride | quote }}
    app.kubernetes.io/instance: {{ .Release.Name | quote }}
    app.kubernetes.io/version: {{ default .Chart.AppVersion .Values.image.tag | quote }}
    helm.sh/chart: {{ printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | quote }}

# ConfigMap with safe values
data:
  DATABASE_URL: {{ printf "postgresql://%s:%s@%s:%d/%s"
    (default "postgres" .Values.db.user)
    (default "password" .Values.db.password)
    (default "localhost" .Values.db.host)
    (default 5432 .Values.db.port | int)
    (default "mydb" .Values.db.name) | quote }}

Helper Template Pattern

{{/* templates/_helpers.tpl */}}

{{/* Generate image reference */}}
{{- define "myapp.image" -}}
{{ print (default "docker.io" .Values.image.registry) "/" .Values.image.repository ":" (default .Chart.AppVersion .Values.image.tag) }}
{{- end }}

{{/* Generate fullname with defaults */}}
{{- define "myapp.fullname" -}}
{{ printf "%s-%s" .Release.Name (default .Chart.Name .Values.fullnameOverride) | trunc 63 | trimSuffix "-" }}
{{- end }}

Common Issues

Best Practices

• Always `quote` annotations and labels — prevents YAML parsing surprises
• Use `default` for every optional value — makes charts self-documenting
• Prefer `printf` over `print` — format strings are more readable
• Quote numeric strings — version numbers, port strings, boolean-like values
• Chain functions with pipes — `{{ .Values.name | default “app” | quote }}`
• Test with `helm template` — always verify output before deploying

Key Takeaways

• `print` concatenates without spaces (vs `cat` which adds spaces)
• `printf` uses Go format verbs (`%s`, `%d`) for structured string formatting
• `quote` wraps in double quotes and escapes — essential for YAML safety
• `default` provides fallback for empty/nil/zero/false values
• Combine all three for robust, self-documenting Helm templates