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5.8.3 The variables extension

The ‘variables’ extension is defined in RFC 5229. It is a built-in extension. It introduces support for variables in Sieve scripts.

There are two kind of variables: user-defined and match variables.

A user-defined variable is initialized using the set action:

Action: set [modifiers] name(string) value(string)

Stores the specified value in the variable identified by name. Optional modifiers are applied on value before it is stored in the variable.

The following modifiers are available:

:lower

Convert value to lower case letters.

:upper

Convert value to upper case letters.

:lowerfirst

Convert the first character in value to lower case.

:upperfirst

Convert the first character in value to upper case.

:quotewildcard

Quote wildcard characters (‘*’, ‘?’, ‘\’) by prefixing each occurrence with a backslash (‘\’). This can be used to ensure that the variable will only match a literal occurrence if used as a parameter to :matches.

:length

The value is the decimal number of characters in the expansion, converted to a string.

When several modifiers are present, they are applied in the following order of precedence (largest value first):

precedence	modifiers
40	:lower or :upper
30	:lowerfirst or :upperfirst
20	:quotewildcard
10	:length

Modifiers having the same precedence (i.e. listed on the same row in the above table) cannot be used together.

Variables are referenced within text strings using the construct ‘${name}’, where name is the name of the variable as it appeared in the first parameter to the set statement. For example:

require "variables";

set "sender" "root
":

if envelope :matches "${sender}"
{
   ...
}

Match variables refer to parts of the most recently evaluated successful match of type :matches or :regex. They have names consisting entirely of decimal digits. The variable ‘${0}’ refers to the entire matched expression. The variable ‘${1}’ refers to the substring matching the first occurrence of the wildcard (‘?’ and ‘*’), ‘${2}’ refers to the second occurrence and so on. The wildcards match as little as possible (non-greedy matching). For example:

require ["variables", "fileinto"];

if header :matches "List-ID" "*<*
" {
   fileinto "INBOX.lists.${2}";
   stop;
}

If :regex match is used, the match variables starting from ‘${1}’ refer to the substrings of the argument value matching subsequent parenthesized groups of the regular expression.

Test: string [comparator] [match-type] source(string-list) keys(string-list)

The string test compares two strings according to the selected comparator and match type. The test evaluates to ‘true’ if any two strings from source and keys match.

The ‘:count’ match used in ‘string’ counts each empty string as 0, and each non-empty one as 1. The count of a string list is the sum of the counts of the member strings.