Operators

Dasel supports a range of operators for arithmetic, comparison, logic, assignment, and pattern matching.

Arithmetic Operators

Arithmetic operators work on numeric values (int and float). If either operand is a float, the result is a float.

Operator	Description	Example	Result
+	Addition	3 + 2	5
-	Subtraction	10 - 4	6
*	Multiplication	3 * 4	12
/	Division	10 / 3	3
%	Modulo	10 % 3	1

The + operator also works for string concatenation.

Examples

5 + 3    // 8
10 - 4   // 6
3 * 4    // 12
10 / 3   // 3 (integer division)
10 / 3.0 // 3.333... (float division)
10 % 3   // 1

Comparison Operators

Comparison operators return a boolean value.

Operator	Description	Example	Result
==	Equal	1 == 1	true
!=	Not equal	1 != 2	true
>	Greater than	3 > 2	true
>=	Greater than or equal	3 >= 3	true
<	Less than	2 < 3	true
<=	Less than or equal	3 <= 3	true
=~	Like (regex match)	"foo" =~ r/^f/	true
!~	Not like (regex no match)	"foo" !~ r/^b/	true

Examples

"hello" == "hello" // true
"hello" != "world" // true
5 > 3              // true
5 >= 5             // true
2 < 3              // true
3 <= 3             // true
"bar" =~ r/^b/     // true
"bar" !~ r/^f/     // true

See Regex for more on pattern matching.

Logical Operators

Logical operators combine boolean expressions.

Operator	Description	Example	Result
&&	And	true && false	false
||	Or	true || false	true

Examples

age > 18 && age < 65   // true if age is between 18 and 65
name == "Tom" || name == "Jim"  // true if name is either

Assignment Operator

The = operator assigns a value. It can be used to set variables, modify fields, or update array elements.

Operator	Description	Example
=	Assign	foo.bar = "new"

Examples

Set a variable

$name = "Tom";
$name
// "Tom"

Modify a field

$ echo '{"name": "old"}' | dasel -i json --root 'name = "new"'
{
    "name": "new"
}

Modify in a loop

$ echo '[1, 2, 3]' | dasel -i json 'each($this = $this + 10)'
[11, 12, 13]

See Modifying data for more details.

Coalesce Operator

The ?? operator provides a fallback value when the left side is null, missing, or errors.

Operator	Description	Example
??	Coalesce	foo.bar ?? "default"

See Coalesce for full documentation.

Spread Operator

The ... operator unpacks arrays or maps into their individual elements.

Operator	Description	Example
...	Spread	[1, 2, 3].sum($this...)

See Spread for full documentation.