Provided by: postfix-pcre_3.9.0-3_amd64 
NAME
pcre_table - format of Postfix PCRE tables
SYNOPSIS
postmap -q "string" pcre:/etc/postfix/filename
postmap -q - pcre:/etc/postfix/filename <inputfile
postmap -hmq - pcre:/etc/postfix/filename <inputfile
postmap -bmq - 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. Use "postmap -hmq
- <file" for header_checks(5) patterns, and "postmap -bmq - <file" for body_checks(5) (Postfix 2.6 and
later).
This driver can be built with the pcre2 library (Postfix 3.7 and later), or with the legacy pcre library
(all Postfix versions).
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 If the input string matches /pattern/, then match that input string against the patterns between
if and endif. 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 If the input string does not match /pattern/, then match that input string against the patterns
between if and endif. 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-alphanumeric
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 the pcre MULTILINE flag is set.
U (default: off)
Toggles the pcre UNGREEDY 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.
This feature is not supported with PCRE2.
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 $$ to produce a $ character as output. The macros
in the result string may need to be written as ${n} or $(n) if they aren't followed by whitespace. This
feature does not support pcre2 substring names.
Note: since negated patterns (those preceded by !) return a result when the expression does not match,
substitutions are not available for negated patterns.
INLINE SPECIFICATION
The contents of a table may be specified in the table name (Postfix 3.7 and later). The basic syntax is:
main.cf:
parameter = .. pcre:{ { rule-1 }, { rule-2 } .. } ..
master.cf:
.. -o { parameter = .. pcre:{ { rule-1 }, { rule-2 } .. } .. } ..
Postfix ignores whitespace after '{' and before '}', and writes each rule as one text line to an
in-memory file:
in-memory file:
rule-1
rule-2
..
Postfix parses the result as if it is a file in /etc/postfix.
Note: if an inlined rule contains $, specify $$ to keep Postfix from trying to do $name expansion as it
evaluates a parameter value.
Note: when using $name inside an inlined pattern, use \Q$name\E to disable metacharacters such as '.' in
the $name expansion. Otherwise, the pattern may have unexpected matches.
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
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
PCRE_TABLE(5)