= Double-Quoted Strings

.Syntax
`"string"`

A double-quoted string is interpreted via the usual rules in
programming languages for double quoted strings. The double-quote
character can be placed in a string by escaping it with a backslash.
Carriage returns and line-feeds can also be used via the usual `\r` and
`\n` syntax.

The main difference between the single and double quoted strings is
that the double quoted strings can be dynamically expanded. The syntax
`${...}` is used for parse-time expansion and `%{...}` is used for
run-time expansion. The difference between the two methods is that the
`${...}` form is expanded when the server loads the configuration
files and is valid anywhere in the configuration files. The `%{...}`
link:xlat.adoc[string expansion] form is valid only in conditional
expressions and attribute assignments.

The output of the dynamic expansion can be interpreted as a string,
a number, or an IP address, depending on its context.

Note that the interpretation of text _strongly_ depends on the
context.  The text `"0000"` can be interpreted as a data type
"integer", having value zero, or a data type "string", having value
`"0000"`.  In general when a particular piece of text is used, it is
used with the context of a known attribute.  That attribute has a
link:data.adoc[data type], and the text will be interpreted as that
data type.

.Examples

`"word"` +
`"a string"` +
`"this has embedded\ncharacters"`

// Copyright (C) 2020 Network RADIUS SAS.  Licenced under CC-by-NC 4.0.
// Development of this documentation was sponsored by Network RADIUS SAS.