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= The switch Statement
.Syntax
[source,unlang]
----
switch <expansion> {
case <match-1> {
[ statements-1 ]
}
case <match-2> {
[ statements-2 ]
}
case {
[ statements-3 ]
}
}
----
A `switch` statement causes the server to evaluate _expansion_, which
can be an xref:attr.adoc[&Attribute-Name] or
xref:condition/operands.adoc[data]. The result is compared against _match-1_
and _match-2_ to find a match. If no string matches, then the server
looks for the default xref:case.adoc[case] statement, which has no
associated match.
The matching is done via equality. The `switch` statement is mostly
syntactic sugar and is used to simplify the visual form of the
configuration. It is mostly equivalent to the following use of
xref:if.adoc[if] statements:
.Nearly equivalent syntax
[source,unlang]
----
if (<expansion> == <match-1>) {
[ statements-1 ]
}
elsif (<expansion> == <match-2>) {
[ statements-2 ]
}
else {
[ statements-3 ]
}
----
The only difference between the two forms is that for a `switch`
statement, the _expansion_ is evaluated only once. For the equivalent
xref:if.adoc[if] statement, the _expansion_ is evaluated again for every
xref:if.adoc[if].
If a matching xref:case.adoc[case] is found, the statements within
that xref:case.adoc[case] are evaluated. If no matching
xref:case.adoc[case] is found, the `case` section with no "match" is
evaluated. If there is no such `case { ...}` subsection, then the
`switch` statement behaves as if the `case {...}` section was empty.
////
For compatibility with version 3, and empty `case` statement can also
be used instead of `default`.
////
The _match_ text for the xref:case.adoc[case] statement can be an
xref:attr.adoc[&Attribute-Name] or xref:type/index.adoc[data].
No statement other than xref:case.adoc[case] can appear in a `switch`
statement, and the xref:case.adoc[case] statement cannot appear outside of a
`switch` statement.
.Example
[source,unlang]
----
switch &User-Name {
case "bob" {
reject
}
case {
ok
}
}
----
// Copyright (C) 2020 Network RADIUS SAS. Licenced under CC-by-NC 4.0.
// Development of this documentation was sponsored by Network RADIUS SAS.
|
