Core Functionality

Before to check examples, we need to know about comments and whitespace.

{{/* a comment */}}
{{- /* a comment with white space trimmed from preceding and following text */ -}}
	A comment; discarded. May contain newlines.
	Comments do not nest and must start and end at the
	delimiters, as shown here.

Minus sign (-) is a special character that represents white space trimming.

Merhaba

 	{{- " " -}}
  	       dünya!

Output:

Merhaba dünya!

Variables

Inside of template, we can use variables. Variables are defined by $variableName := value syntax.

{{ $x := "Merhaba" -}}
{{ $x }} dünya!

Output:

Merhaba dünya!

For loop

If you have a list of items, you can iterate over them using the range function.

list:
- "item-1"
- "item-2"

Range of list
{{ range $index, $element := .list -}}
{{ $index }}: {{ $element }}
{{ end }}

Output:

Range of list
0: item-1
1: item-2

If we want to for loop with a map, in that time $index is a key of map and $element is a value of map.

We can also use range to count up to a number. But we need to use until function and it's a part of sprig functions. Mugo has a sprig function set by default so we can use it.

Count up to 5
{{ range $index, $element := until 5 -}}
{{ $index }}: {{ $element }}
{{ end }}

Output:

Count up to 5
0: 0
1: 1
2: 2
3: 3
4: 4

If statement

Binary check functions eq, ne, lt, le, gt, ge but arguments should comparable types and result is boolean.

result: 10

{{if eq .result 10 -}}
Result is 10
{{- else if eq .result 0 -}}
Result is 0
{{- else -}}
unknown
{{- end}}

Output:

Result is 10

Index

We can use index function to get an item from a list.

list:
 - "item-1"
 - "item-2"

First item of list: {{ index .list 0 }}

Output:

First item of list: item-1

Define

We can use define to define a template and use it later with template function and giving variables.

{{- define "hello" -}}
Hello {{ .name }}
{{- end -}}

{{ template "hello" . }}

Output:

Merhaba dünya!

With

Use with to limit the scope of a variable inside of a template.

If name value is empty, it will not print anything.

{{ with .name -}}
Merhaba {{ . }}
{{- end }}

If we want to reach outer scope, we can use $. syntax.

{{ with .name -}}
Item {{ . }} value is {{ $.value }}
{{- end }}

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Examples

Some useful examples with templates.

Sum of variables

addf function is a part of sprig functions. It uses decimal library to calculate floating point numbers.

values:
 - 6.1
 - 5.81
 - 7.9

{{ $sum := 0 -}}
{{ range $index, $element := .values -}}
{{ $sum = addf $sum $element -}}
{{ end -}}
Total value {{ $sum }}

Output:

Total value 19.81