Provided by: postfix_2.11.0-1ubuntu1.2_amd64 
NAME
pcre_table - format of Postfix PCRE tables
SYNOPSIS
postmap -q "string" pcre:/etc/postfix/filename
postmap -q - pcre:/etc/postfix/filename <inputfile
DESCRIPTION
The Postfix mail system uses optional tables for address rewriting, mail routing, or
access control. These tables are usually in dbm or db format.
Alternatively, lookup tables can be specified in Perl Compatible Regular Expression form.
In this case, each input is compared against a list of patterns. When a match is found,
the corresponding result is returned and the search is terminated.
To find out what types of lookup tables your Postfix system supports use the "postconf -m"
command.
To test lookup tables, use the "postmap -q" command as described in the SYNOPSIS above.
COMPATIBILITY
With Postfix version 2.2 and earlier specify "postmap -fq" to query a table that contains
case sensitive patterns. Patterns are case insensitive by default.
TABLE FORMAT
The general form of a PCRE table is:
/pattern/flags result
When pattern matches the input string, use the corresponding result value.
!/pattern/flags result
When pattern does not match the input string, use the corresponding result value.
if /pattern/flags
endif Match the input string against the patterns between if and endif, if and only if
that same input string also matches pattern. The if..endif can nest.
Note: do not prepend whitespace to patterns inside if..endif.
This feature is available in Postfix 2.1 and later.
if !/pattern/flags
endif Match the input string against the patterns between if and endif, if and only if
that same input string does not match pattern. The if..endif can nest.
Note: do not prepend whitespace to patterns inside if..endif.
This feature is available in Postfix 2.1 and later.
blank lines and comments
Empty lines and whitespace-only lines are ignored, as are lines whose first non-
whitespace character is a `#'.
multi-line text
A logical line starts with non-whitespace text. A line that starts with whitespace
continues a logical line.
Each pattern is a perl-like regular expression. The expression delimiter can be any non-
alphanumerical character, except whitespace or characters that have special meaning
(traditionally the forward slash is used). The regular expression can contain whitespace.
By default, matching is case-insensitive, and newlines are not treated as special
characters. The behavior is controlled by flags, which are toggled by appending one or
more of the following characters after the pattern:
i (default: on)
Toggles the case sensitivity flag. By default, matching is case insensitive.
m (default: off)
Toggles the PCRE_MULTILINE flag. When this flag is on, the ^ and $ metacharacters
match immediately after and immediately before a newline character, respectively,
in addition to matching at the start and end of the subject string.
s (default: on)
Toggles the PCRE_DOTALL flag. When this flag is on, the . metacharacter matches
the newline character. With Postfix versions prior to 2.0, the flag is off by
default, which is inconvenient for multi-line message header matching.
x (default: off)
Toggles the pcre extended flag. When this flag is on, whitespace characters in the
pattern (other than in a character class) are ignored. To include a whitespace
character as part of the pattern, escape it with backslash.
Note: do not use #comment after patterns.
A (default: off)
Toggles the PCRE_ANCHORED flag. When this flag is on, the pattern is forced to be
"anchored", that is, it is constrained to match only at the start of the string
which is being searched (the "subject string"). This effect can also be achieved by
appropriate constructs in the pattern itself.
E (default: off)
Toggles the PCRE_DOLLAR_ENDONLY flag. When this flag is on, a $ metacharacter in
the pattern matches only at the end of the subject string. Without this flag, a
dollar also matches immediately before the final character if it is a newline
character (but not before any other newline characters). This flag is ignored if
PCRE_MULTILINE flag is set.
U (default: off)
Toggles the ungreedy matching flag. When this flag is on, the pattern matching
engine inverts the "greediness" of the quantifiers so that they are not greedy by
default, but become greedy if followed by "?". This flag can also set by a (?U)
modifier within the pattern.
X (default: off)
Toggles the PCRE_EXTRA flag. When this flag is on, any backslash in a pattern that
is followed by a letter that has no special meaning causes an error, thus reserving
these combinations for future expansion.
SEARCH ORDER
Patterns are applied in the order as specified in the table, until a pattern is found that
matches the input string.
Each pattern is applied to the entire input string. Depending on the application, that
string is an entire client hostname, an entire client IP address, or an entire mail
address. Thus, no parent domain or parent network search is done, and user@domain mail
addresses are not broken up into their user and domain constituent parts, nor is user+foo
broken up into user and foo.
TEXT SUBSTITUTION
Substitution of substrings (text that matches patterns inside "()") from the matched
expression into the result string is requested with $1, $2, etc.; specify $$ to produce a
$ character as output. The macros in the result string may need to be written as ${n} or
$(n) if they aren't followed by whitespace.
Note: since negated patterns (those preceded by !) return a result when the expression
does not match, substitutions are not available for negated patterns.
EXAMPLE SMTPD ACCESS MAP
# Protect your outgoing majordomo exploders
/^(?!owner-)(.*)-outgoing@(.*)/ 550 Use ${1}@${2} instead
# Bounce friend@whatever, except when whatever is our domain (you would
# be better just bouncing all friend@ mail - this is just an example).
/^(friend@(?!my\.domain$).*)$/ 550 Stick this in your pipe $1
# A multi-line entry. The text is sent as one line.
#
/^noddy@my\.domain$/
550 This user is a funny one. You really don't want to send mail to
them as it only makes their head spin.
EXAMPLE HEADER FILTER MAP
/^Subject: make money fast/ REJECT
/^To: friend@public\.com/ REJECT
EXAMPLE BODY FILTER MAP
# First skip over base 64 encoded text to save CPU cycles.
# Requires PCRE version 3.
~^[[:alnum:]+/]{60,}$~ OK
# Put your own body patterns here.
SEE ALSO
postmap(1), Postfix lookup table manager
postconf(5), configuration parameters
regexp_table(5), format of POSIX regular expression tables
README FILES
Use "postconf readme_directory" or "postconf html_directory" to locate this information.
DATABASE_README, Postfix lookup table overview
AUTHOR(S)
The PCRE table lookup code was originally written by:
Andrew McNamara
andrewm@connect.com.au
connect.com.au Pty. Ltd.
Level 3, 213 Miller St
North Sydney, NSW, Australia
Adopted and adapted by:
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
PCRE_TABLE(5)