Sprig Functions

String Manipulation Math Functions Date Formatting Default & Required

A comprehensive guide to Sprig functions in Helm covering string manipulation, math operations, date formatting, default, required, and advanced template functions.

String Functions Math Functions Date Functions Default & Required

What is Sprig?

Sprig is a library of over 60 template functions for Go templates. Helm includes all Sprig functions, providing powerful capabilities for string manipulation, math operations, date formatting, and more.

Sprig functions are available in all Helm templates and can be chained using pipelines.

Key Concept: Sprig functions are the "Swiss Army knife" of Helm templating. They provide essential utilities that make templates more expressive and powerful.

String Manipulation Functions

upper / lower

Convert strings to uppercase/lowercase.

{{ "hello" | upper }} → HELLO {{ "WORLD" | lower }} → world

trim

Remove leading and trailing whitespace.

{{ " hello " | trim }} → hello

trunc

Truncate a string to a specified length.

{{ "hello world" | trunc 5 }} → hello

replace

Replace all occurrences of a substring.

{{ "hello world" | replace "world" "there" }} → hello there

contains

Check if a string contains a substring.

{{ contains "hello" "hel" }} → true

hasPrefix / hasSuffix

Check if a string starts or ends with a prefix/suffix.

{{ hasPrefix "hello" "he" }} → true

trimPrefix / trimSuffix

Remove a prefix/suffix from a string.

{{ "hello" | trimSuffix "o" }} → hell

quote / squote

Wrap a string in double/single quotes.

{{ "hello" | quote }} → "hello"

                # String function examples

# upper/lower
{{ "hello" | upper }}       # HELLO
{{ "WORLD" | lower }}       # world

# trim
{{ "  hello  " | trim }}    # hello

# trunc
{{ "hello world" | trunc 5 }} # hello

# replace
{{ "hello world" | replace "world" "there" }} # hello there

# contains
{{ contains "hello" "hel" }} # true

# hasPrefix/hasSuffix
{{ hasPrefix "hello" "he" }} # true
{{ hasSuffix "hello" "lo" }} # true

# trimPrefix/trimSuffix
{{ "hello" | trimSuffix "o" }} # hell
{{ "hello" | trimPrefix "he" }} # llo

# quote/squote
{{ "hello" | quote }}        # "hello"
{{ "hello" | squote }}       # 'hello'

# split (split into list)
{{ split "a,b,c" "," }}      # [a b c]

# join (join list with separator)
{{ list "a" "b" "c" | join "," }} # a,b,c

# regexReplaceAll
{{ "Hello World" | regexReplaceAll "World" "There" }} # Hello There

# toString
{{ 123 | toString }}         # "123"
            

Math Functions

add / sub / mul / div

Basic arithmetic operations.

{{ add 5 3 }} → 8 {{ sub 10 4 }} → 6

floor / ceil

Round down/up to nearest integer.

{{ floor 5.7 }} → 5 {{ ceil 5.2 }} → 6

abs / max / min

Absolute value, maximum, minimum.

{{ abs -5 }} → 5 {{ max 1 5 3 }} → 5

mod

Modulo operation.

{{ mod 10 3 }} → 1

pow / sqrt

Power and square root.

{{ pow 2 3 }} → 8 {{ sqrt 16 }} → 4

                # Math function examples

# add/sub/mul/div
{{ add 5 3 }}      # 8
{{ sub 10 4 }}     # 6
{{ mul 3 4 }}      # 12
{{ div 10 2 }}     # 5

# floor/ceil
{{ floor 5.7 }}    # 5
{{ ceil 5.2 }}     # 6
{{ round 5.55 }}   # 6

# abs/max/min
{{ abs -5 }}       # 5
{{ max 1 5 3 }}    # 5
{{ min 1 5 3 }}    # 1

# mod
{{ mod 10 3 }}     # 1

# pow/sqrt
{{ pow 2 3 }}      # 8
{{ sqrt 16 }}      # 4

# inc/dec (increment/decrement)
{{ inc 5 }}        # 6
{{ dec 5 }}        # 4

# add1/sub1 (alternatives)
{{ add1 5 }}       # 6
{{ sub1 5 }}       # 4
            

Date and Time Functions

now

Get the current time.

{{ now }} → 2024-01-15 10:30:00 ...

date

Format a date using a layout string.

{{ now | date "2006-01-02" }} → 2024-01-15

dateModify

Add or subtract duration from a date.

{{ now | dateModify "+24h" }} → tomorrow

toDate

Parse a string into a date.

                # Date function examples

# now (current time)
{{ now }}

# date (format)
{{ now | date "2006-01-02" }}           # 2024-01-15
{{ now | date "2006-01-02 15:04:05" }}  # 2024-01-15 10:30:00
{{ now | date "Mon Jan 2 15:04:05 MST 2006" }}

# dateModify (add/subtract duration)
{{ now | dateModify "+24h" }}           # Tomorrow
{{ now | dateModify "-7d" }}            # 7 days ago
{{ now | dateModify "+1h" }}            # 1 hour from now

# toDate (parse string to date)
{{ "2024-01-15" | toDate "2006-01-02" }}
{{ "2024-01-15T10:30:00Z" | toDate "2006-01-02T15:04:05Z" }}

# date comparison
{{ $date := "2024-01-15" | toDate "2006-01-02" }}
{{ $today := now | date "2006-01-02" | toDate "2006-01-02" }}
{{ if $date.Before $today }}before{{ else }}after{{ end }}

# Unix timestamp
{{ now | unixEpoch }}  # 1705330000
            

Date Formatting Note: Go uses a specific reference time for formatting: Mon Jan 2 15:04:05 MST 2006. This is not a placeholder—it's the actual format used by Go's time package.

Default and Required Functions

default

Provide a fallback value if the input is empty.

required

Require a value; fail with an error message if missing.

empty

Check if a value is empty (nil, empty string, empty list, etc.).

{{ if empty .Values.optional }}empty{{ end }}

hasKey

Check if a map has a specific key.

                # default - fallback values
{{ .Values.image.tag | default "latest" }}
{{ .Values.replicaCount | default 1 }}
{{ .Values.environment | default "dev" }}

# default with condition
{{ .Values.ingress.enabled | default false }}

# required - mandatory values
{{ required "A valid database URL is required" .Values.database.url }}
{{ required "A valid image repository is required" .Values.image.repository }}

# empty - check for empty values
{{ if empty .Values.optionalValue }}
  # Value is empty
{{ end }}

# hasKey - check if key exists
{{ if hasKey .Values "database" }}
  # Database key exists
{{ end }}

# coalesce - first non-empty value
{{ coalesce .Values.region .Values.zone .Values.area "default" }}

# ternary - conditional operator
{{ ternary "enabled" "disabled" .Values.feature.enabled }}
            

Best Practice: Use default for optional values and required for mandatory values. This makes charts more robust and provides clear error messages for missing configuration.

Advanced Sprig Functions

                # List/Array functions
{{ list "a" "b" "c" }}          # Create list
{{ list 1 2 3 | first }}         # First item (1)
{{ list 1 2 3 | last }}          # Last item (3)
{{ list 1 2 3 | rest }}          # All except first ([2 3])
{{ list 1 2 3 | append 4 }}      # Add item ([1 2 3 4])
{{ list 1 2 3 | prepend 0 }}     # Add at beginning ([0 1 2 3])
{{ list 1 2 3 | reverse }}       # Reverse list ([3 2 1])
{{ len (list 1 2 3) }}           # Length (3)

# Dictionary functions
{{ dict "key" "value" }}         # Create dict
{{ get .Values "key" }}          # Get value from dict
{{ set .Values "key" "value" }}  # Set value in dict
{{ unset .Values "key" }}        # Remove key from dict
{{ hasKey .Values "key" }}       # Check if key exists

# Type conversion
{{ 123 | toString }}             # "123"
{{ "123" | toInt }}              # 123
{{ "123" | toFloat }}            # 123.0
{{ "123" | toInt64 }}            # 123

# UUID generation
{{ uuidv4 }}                     # Generate UUID

# Random functions
{{ randNumeric }}                # Random number
{{ randNumeric 5 }}              # 5-digit random number
{{ randAlphaNum 10 }}            # 10-character alphanumeric string

# Environment variables
{{ env "HOME" }}                 # Get environment variable

# Base64 encoding
{{ "hello" | b64enc }}           # Base64 encode
{{ "aGVsbG8=" | b64dec }}        # Base64 decode
            

Advanced Tip: Sprig also provides functions for working with cryptographic hashes (sha256, sha1), JSON/YAML operations, and network-related utilities. Check the Sprig documentation for the complete list.

Frequently Asked Questions

What is Sprig and why is it important in Helm?

Sprig is a library of template functions for Go templates. Helm includes all Sprig functions, providing powerful utilities for string manipulation, math, date formatting, and more. It makes Helm templates more expressive and powerful.

What is the difference between default and required?

default provides a fallback value if the input is empty. required fails with an error message if the value is missing. Use default for optional values and required for mandatory values.

How do I format dates in Helm?

Use date with a layout string: {{ now | date "2006-01-02" }}. Go uses the reference time Mon Jan 2 15:04:05 MST 2006 for formatting.

Can I do math in Helm templates?

Yes! Sprig provides math functions like add, sub, mul, div, floor, ceil, max, min, and more.

What string manipulation functions are available?

Sprig provides upper, lower, trim, trunc, replace, contains, hasPrefix, hasSuffix, trimPrefix, trimSuffix, quote, and more.

How do I check if a value is empty in Helm?

Use the empty function: {{ if empty .Values.optional }}empty{{ end }}. This works for strings, lists, maps, and other types.

Can I generate UUIDs in Helm?

Yes! Use {{ uuidv4 }} to generate a UUID v4 string. This is useful for generating unique identifiers.

How do I work with lists in Helm?

Use list to create lists, and functions like first, last, rest, append, prepend, reverse, and len to manipulate them.