PCRE_TABLE(5) PCRE_TABLE(5)
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 Com-
patible 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 sys-
tem 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 cor-
responding 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 logi-
cal line.
Each pattern is a perl-like regular expression. The
expression delimiter can be any character, except white-
space or characters that have special meaning (tradition-
ally 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 con-
trolled 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 in the pattern (other than in a
character class) and characters between a # outside
a character class and the next newline character
are ignored. An escaping backslash can be used to
include a whitespace or # character as part of the
pattern.
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 immedi-
ately before the final character if it is a newline
character (but not before any other newline charac-
ters). 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 fol-
lowed 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 expan-
sion.
SEARCH ORDER
Patterns are applied in the order as specified in the ta-
ble, 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 from the matched expression
into the result string is possible using the conventional
perl syntax ($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
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)