Appendix D: Regular expressions : Syntax
Syntax
Table 68 lists some example regular expressions, and describes matches for each expression. Regular expressions on FortiMail units use Perl-style syntax.
 
Table 68: Regular expression syntax 
Expression
Matches
abc
abc (the exact character sequence, but anywhere in the string)
^abc
abc at the beginning of the string
abc$
abc at the end of the string
a|b
Either a or b
^abc|abc$
abc at either the beginning or the end of the string
ab{2,4}c
a followed by two, three or four b characters, followed by c
ab{2,}c
a followed by at least two “b”s followed by a “c”
ab*c
a followed by any number (zero or more) of “b”s followed by a “c”
ab+c
a followed by one or more b's followed by a c
ab?c
a followed by an optional “b” followed by a” c”; that is, either “abc” or “ac”
a.c
a followed by any single character (not newline) followed by a “c”
a\.c
a.c
[abc]
Any one of a, b or c
[Aa]bc
Either Abc or abc
[abc]+
Any combination of one or more a, b, and/or c characters (such as a, abba, or acbabcacaa)
[^abc]+
Any combination of one or more characters that does not contain an a, b, and/or c (such as defg)
\d\d
Any two decimal digits, such as 42; same as \d{2}
\w+
A word (a non-empty sequence of alphanumeric characters and underscores), such as foo, 12bar8, or foo_1
100\s*mk
100 and mk separated by zero or more white space characters (spaces, tabs, newlines)
abc\b
abc when followed by a word boundary (for example, abc! but not abcd)
start\B
start when not followed by a word boundary (for example, starting but not start time)
\x
Ignores white space that is neither preceded by a backslash character nor within a character class. Use this to break up a regular expression into (slightly) more readable parts.
/x
Used to add regular expressions within other text. If the first character in a pattern is forward slash (/), the / is treated as the delimiter. The pattern must contain a second /. The pattern between / will be taken as a regular expression, and anything after the second / will be parsed as a list of regular expression options (i, x, etc). An error occurs If the second / is missing. In regular expressions, the leading and trailing space is treated as part of the regular expression.