PCRE_TABLE(5)PCRE_TABLE(5)NAMEpcre_table - format of Postfix PCRE tables
SYNOPSIS
postmap -fq "string" pcre:/etc/postfix/filename
postmap -fq - pcre:/etc/postfix/filename <inputfile
DESCRIPTION
The Postfix mail system uses optional tables for address rewriting or
mail routing. These tables are usually in dbm or db format.
Alternatively, lookup tables can be specified in Perl Compatible Regu‐
lar Expression form. In this case, each input is compared against a
list of patterns, and when a match is found the corresponding result is
returned.
To find out what types of lookup tables your Postfix system supports
use the "postconf -m" command.
To test lookup tables, use the "postmap -fq" command as described in
the SYNOPSIS above.
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 corre‐
sponding result value.
if /pattern/flags
endif Match the input string against the patterns between if and
endif, if and only if the 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 the 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 delim‐
iter can be any 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 ver‐
sions prior to 2.0, The flag is off by default, which is incon‐
venient 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 char‐
acter 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 pat‐
tern 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 sub‐
ject 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 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 quanti‐
fiers 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 back‐
slash in a pattern that is followed by a letter that has no spe‐
cial 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 par‐
ent network search is done, and user@domain mail addresses are not bro‐
ken 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 ALSOpostmap(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)
