Operands

Syntax

string
integer
"double-quoted string"
'single-quoted string'
`back-quoted string`

Any text not matching Attribute-Name or a return code is interpreted as a value for a particular data type.

Double-quoted strings and back-quoted strings are dynamically expanded before the condition is evaluated. Single-quoted strings are static literals and are not dynamically expanded.

When used as an existence check, the condition evaluates to true if the data is non-zero. Otherwise, the condition evaluates to false.

For integer existence checks, 0 is false; all other values are true.

For string existence checks, an empty string is false. All other strings are true.

Table 1. Data Types Truthiness
Type	True When
Bool	Value is true
String, octets	Length > 0
Group	Has at least one element
Ipv4addr, ipv6addr	Not INADDR_ANY (not 0.0.0.0 / ::)
Ipv4prefix, ipv6prefix	Not 0.0.0.0/0 or ::/0
Integers, float32, float64	Cast to bool is true (non-zero)
Ifid, ethernet	Cast to bool is true (non-zero)

All other data types are disallowed in existence checks.

Examples

"hello there"
5