Postfix manual - pcre_table(5)

    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 Regu-
           lar 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 sensitive patterns. Patterns are case insensi-
           tive 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 corre-
                  sponding 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 pat-
                  tern. 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 pat-
                  tern. 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  non-alphanumerical  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
                  characters in the pattern (other than in a character class)  are
                  ignored.   To include a whitespace character as part of the pat-
                  tern, 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  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 (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.

           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)