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 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 sensi-
tive 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 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 charac-ters characters
ters 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 imme-diately immediately
diately after and immediately before a newline character, respectively, in addition to match-ing matching
ing 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 inconve-nient inconvenient
nient 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 # charac-ter character
ter 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 pat-tern pattern
tern 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 imme-diately immediately
diately before the final character if it is a newline character (but not before any other new-line newline
line 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 fol-lowed followed
lowed by a letter that has no special meaning causes an error, thus reserving these combina-tions combinations
tions 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 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
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)
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