redhat man page for pipe

PIPE(8) 						      System Manager's Manual							   PIPE(8)

NAME
       pipe - Postfix delivery to external command

SYNOPSIS
       pipe [generic Postfix daemon options] command_attributes...

DESCRIPTION
       The pipe daemon processes requests from the Postfix queue manager to deliver messages to external commands.  This program expects to be run
       from the master(8) process manager.

       Message attributes such as sender address, recipient address and next-hop host name can	be  specified  as  command-line  macros  that  are
       expanded before the external command is executed.

       The  pipe  daemon updates queue files and marks recipients as finished, or it informs the queue manager that delivery should be tried again
       at a later time. Delivery problem reports are sent to the bounce(8) or defer(8) daemon as appropriate.

SINGLE-RECIPIENT DELIVERY
       Some external commands cannot handle more than one recipient per delivery request. Examples of such transports are  pagers,  fax  machines,
       and so on.

       To prevent Postfix from sending multiple recipients per delivery request, specify

	   transport_destination_recipient_limit = 1

       in  the	Postfix  main.cf  file, where transport is the name in the first column of the Postfix master.cf entry for the pipe-based delivery
       transport.

COMMAND ATTRIBUTE SYNTAX
       The external command attributes are given in the master.cf file at the end of a service definition.  The syntax is as follows:

       flags=BFRhqu.> (optional)
	      Optional message processing flags. By default, a message is copied unchanged.

	      B      Append a blank line at the end of each message. This is required by some mail user agents that recognize "From "  lines  only
		     when preceded by a blank line.

	      F      Prepend a "From sender time_stamp" envelope header to the message content.  This is expected by, for example, UUCP software.

	      R      Prepend a Return-Path: message header with the envelope sender address.

	      h      Fold  the	command-line  $recipient  domain  name and $nexthop host name to lower case.  This is recommended for delivery via
		     UUCP.

	      q      Quote white space and other special characters in the command-line $sender and $recipient address	localparts  (text  to  the
		     left  of the right-most @ character), according to an 8-bit transparent version of RFC 822.  This is recommended for delivery
		     via UUCP or BSMTP.

		     The result is compatible with the address parsing of command-line recipients by the Postfix sendmail mail submission command.

		     The q flag affects only entire addresses, not the partial address information from the $user, $extension or $mailbox command-
		     line macros.

	      u      Fold  the	command-line $recipient address localpart (text to the left of the right-most @ character) to lower case.  This is
		     recommended for delivery via UUCP.

	      .      Prepend . to lines starting with ".". This is needed by, for example, BSMTP software.

	      >      Prepend > to lines starting with "From ". This is expected by, for example, UUCP software.

       user=username (required)

       user=username:groupname
	      The external command is executed with the rights of the specified username.  The software refuses  to  execute  commands	with  root
	      privileges,  or  with the privileges of the mail system owner. If groupname is specified, the corresponding group ID is used instead
	      of the group ID of username.

       eol=string (default: 
)
	      The output record delimiter. Typically one would use either 
 or 
. The usual C-style backslash escape sequences are recognized:
	      a  f 
 
 	 v octal and \.

       size=size_limit (optional)
	      Messages greater in size than this limit (in bytes) will be bounced back to the sender.

       argv=command... (required)
	      The  command  to	be executed. This must be specified as the last command attribute.  The command is executed directly, i.e. without
	      interpretation of shell meta characters by a shell command interpreter.

	      In the command argument vector, the following macros are recognized and replaced with corresponding  information	from  the  Postfix
	      queue manager delivery request:

	      ${extension}
		     This  macro expands to the extension part of a recipient address.	For example, with an address user+foo@domain the extension
		     is foo.

		     A command-line argument that contains ${extension} expands into as many command-line arguments as there are recipients.

		     This information is modified by the u flag for case folding.

	      ${mailbox}
		     This macro expands to the complete local part of a recipient address.  For example, with an address user+foo@domain the mail-
		     box is user+foo.

		     A command-line argument that contains ${mailbox} expands into as many command-line arguments as there are recipients.

		     This information is modified by the u flag for case folding.

	      ${nexthop}
		     This macro expands to the next-hop hostname.

		     This information is modified by the h flag for case folding.

	      ${recipient}
		     This macro expands to the complete recipient address.

		     A command-line argument that contains ${recipient} expands into as many command-line arguments as there are recipients.

		     This information is modified by the hqu flags for quoting and case folding.

	      ${sender}
		     This macro expands to the envelope sender address.

		     This information is modified by the q flag for quoting.

	      ${size}
		     This macro expands to Postfix's idea of the message size, which is an approximation of the size of the message as delivered.

	      ${user}
		     This  macro  expands  to the username part of a recipient address.  For example, with an address user+foo@domain the username
		     part is user.

		     A command-line argument that contains ${user} expands into as many command-line arguments as there are recipients.

		     This information is modified by the u flag for case folding.

       In addition to the form ${name}, the forms $name and $(name) are also recognized.  Specify $$ where a single $ is wanted.

DIAGNOSTICS
       Command exit status codes are expected to follow the conventions defined in <sysexits.h>.

       Problems and transactions are logged to syslogd(8).  Corrupted message files are marked so that the queue manager can move them to the cor-
       rupt queue for further inspection.

SECURITY
       This program needs a dual personality 1) to access the private Postfix queue and IPC mechanisms, and 2) to execute external commands as the
       specified user. It is therefore security sensitive.

CONFIGURATION PARAMETERS
       The following main.cf parameters are especially relevant to this program. See the Postfix main.cf file for syntax details and  for  default
       values. Use the postfix reload command after a configuration change.

Miscellaneous
       export_environment
	      List of names of environment parameters that can be exported to non-Postfix processes.

       mail_owner
	      The process privileges used while not running an external command.

Resource controls
       In the text below, transport is the first field in a master.cf entry.

       transport_destination_concurrency_limit
	      Limit  the  number  of parallel deliveries to the same destination, for delivery via the named transport. The default limit is taken
	      from the default_destination_concurrency_limit parameter.  The limit is enforced by the Postfix queue manager.

       transport_destination_recipient_limit
	      Limit the number of recipients per message delivery, for delivery via the named transport. The  default  limit  is  taken  from  the
	      default_destination_recipient_limit parameter.  The limit is enforced by the Postfix queue manager.

       transport_time_limit
	      Limit  the  time	for  delivery  to external command, for delivery via the named transport. The default limit is taken from the com-
	      mand_time_limit parameter.  The limit is enforced by the Postfix queue manager.

SEE ALSO
       bounce(8) non-delivery status reports
       master(8) process manager
       qmgr(8) queue manager
       syslogd(8) system logging

LICENSE
       The Secure Mailer license must be distributed with this software.

AUTHOR(S)
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

																	   PIPE(8)