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Linux 2.6 - man page for pcre_table (linux section 5)

PCRE_TABLE(5)			       File Formats Manual			    PCRE_TABLE(5)

       pcre_table - format of Postfix PCRE tables

       postmap -q "string" pcre:/etc/postfix/filename

       postmap -q - pcre:/etc/postfix/filename <inputfile

       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"

       To test lookup tables, use the "postmap -q" command as described in the SYNOPSIS above.

       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.

       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 (tra-
       ditionally the forward slash is used).  The regular expression can contain whitespace.

       By default, matching is case-insensitive, and newlines are not treated as special  charac-
       ters.  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 char-
	      acter (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.

       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.

       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.

       # 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.
	550 This user is a funny one. You really don't want to send mail to
	them as it only makes their head spin.

       /^Subject: make money fast/     REJECT
       /^To: friend@public\.com/       REJECT

       # First skip over base 64 encoded text to save CPU cycles.
       # Requires PCRE version 3.
       ~^[[:alnum:]+/]{60,}$~	       OK

       # Put your own body patterns here.

       postmap(1), Postfix lookup table manager
       postconf(5), configuration parameters
       regexp_table(5), format of POSIX regular expression tables

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       DATABASE_README, Postfix lookup table overview

       The PCRE table lookup code was originally written by:
       Andrew McNamara
       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


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