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-rw-r--r-- | doc/antora/modules/unlang/pages/type/double.adoc | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/doc/antora/modules/unlang/pages/type/double.adoc b/doc/antora/modules/unlang/pages/type/double.adoc new file mode 100644 index 0000000..6c3e708 --- /dev/null +++ b/doc/antora/modules/unlang/pages/type/double.adoc @@ -0,0 +1,39 @@ += 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. |