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

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

           postmap -bmq - 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. Use "postmap -hmq - <file"  for  header_checks(5)  pat-
           terns,  and  "postmap -bmq - <file" for body_checks(5) (Postfix 2.6 and
           later).

           This driver can be built  with  the  pcre2  library  (Postfix  3.7  and
           later), or with the legacy pcre library (all Postfix versions).

    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  If  the  input  string  matches /pattern/, then match that input
                  string against the patterns between if and endif.  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  If  the  input  string does not match /pattern/, then match that
                  input string against the patterns  between  if  and  endif.  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-alphanumeric character, except whitespace or  char-
           acters  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 the pcre MULTILINE flag is set.

           U (default: off)
                  Toggles the pcre UNGREEDY flag.  When this flag is on, the  pat-
                  tern 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  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.

                  This feature is not supported with PCRE2.

    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.   This feature does not support
           pcre2 substring names.

           Note: since negated patterns (those preceded by !) return a result when
           the  expression  does  not  match,  substitutions are not available for
           negated patterns.

    INLINE SPECIFICATION
           The contents of a table may be specified in the table name (Postfix 3.7
           and later).  The basic syntax is:

           main.cf:
               parameter = .. pcre:{ { rule-1 }, { rule-2 } .. } ..

           master.cf:
               .. -o { parameter = .. pcre:{ { rule-1 }, { rule-2 } .. } .. } ..

           Postfix  ignores  whitespace  after '{' and before '}', and writes each
           rule as one text line to an in-memory file:

           in-memory file:
               rule-1
               rule-2
               ..

           Postfix parses the result as if it is a file in /etc/postfix.

           Note: if an inlined rule contains $, specify $$ to  keep  Postfix  from
           trying to do $name expansion as it evaluates a parameter value.

           Note: when using $name inside an inlined pattern, use \Q$name\E to dis-
           able metacharacters such as '.' in the $name expansion. Otherwise,  the
           pattern may have unexpected matches.

    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

           Wietse Venema
           Google, Inc.
           111 8th Avenue
           New York, NY 10011, USA

                                                                     PCRE_TABLE(5)