Postfix manual - pcre_table(5)

    PCRE_TABLE(5)                                                    PCRE_TABLE(5)

    NAME
           pcre_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 Com-
           patible Regular 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  sys-
           tem 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 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 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 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)