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 Com-
           patible 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 sys-
           tem 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 insensitive by default.

    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 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  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)