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  4. pcre_table(5)

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PCRE_TABLE(5) File Formats Manual 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 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" 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 corresponding
      result value.

  
!/pattern/flags result

  
When pattern does not match the input string, use the
      corresponding result value.

  

  

  

  
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.

  

  

  

  

  
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.

  

  

  
Empty lines and whitespace-only lines are ignored, as are lines whose
      first non-whitespace character is a `#'.

  

  
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 (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:



  

  
Toggles the case sensitivity flag. By default, matching is case
      insensitive.

  

  
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.

  

  
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.

  

  
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.

  

  

  
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.

  

  
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 character (but not before any other
      newline characters). This flag is ignored if PCRE_MULTILINE flag is
    set.

  

  
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.

  

  
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.








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 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




Use "postconf readme_directory" or
    "postconf html_directory" to locate this information.


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