mail_pipe(1M)              (Essential Utilities)              mail_pipe(1M)


   NAME
         mail_pipe - invoke recipient command for incoming mail

   SYNOPSIS
         mail_pipe [ -x debug_level ] -r recipient -R path_to_sender -c
         content_type -S subject

   DESCRIPTION
         When a new mail message arrives, the mail command first checks if the
         recipient's mailbox indicates that the message is to be forwarded
         elsewhere (to some other recipient or as the input to some command).
         If the message is to be piped into a recipient-specified command,
         mail invokes mail_pipe to do some validation and then execute the
         command in the context of the recipient.

         Command-line arguments are:
         -x debug_level    Turn on debugging for this invocation. See the
                           description of the -x option for the mail command
                           for details.
         -r recipient      The recipient's login id.
         -R path_to_sender The return address to the message's originator.
         -c content_type   The value of the Content-Type: header line in the
                           message.
         -S subject        The value of the Subject: header line in the
                           message if present.

         mail_pipe is installed as a setuid-to-root process, thus enabling
         itself to change it's user and group ids to that of the recipient as
         necessary.

         When invoked, mail_pipe performs the following steps (if a step
         fails, the exit code is noted as [N]):
         -  Validate invocation arguments [1].
         -  Verify that recipient name is < 14 characters long [2].
         -  Verify that the setgid flag for the recipient mailbox is set [3].
         -  Open /var/mail/recipient [4].
         -  Verify that recipient's mailbox starts with the string Forward to
            [5].
         -  Find pipe symbol indicating start of command string in recipient
            mailbox [6].
         -  Find entry for recipient in /etc/passwd [7].
         -  Set gid to recipient's gid [8].
         -  Set uid to recipient's uid [9].
         -  Change current directory to recipient's login directory [10].
         -  Allocate space to hold newly exec'ed environment for recipient
            command [11].
         -  Parse the recipient command, performing any %keyword expansions
            required.  See the `Forwarding mail' section of mail(1), for more
            information regarding %keyword substitutions [12].




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   mail_pipe(1M)              (Essential Utilities)              mail_pipe(1M)


         -  Execute recipient command [13 if exec fails, otherwise exit code
            from recipient command itself].

   FILES
        /etc/passwd      to identify sender and locate recipients
        /var/mail/recipient
                          incoming mail for recipient; that is, the mail file
        /tmp/MLDBG*      debug trace file
        /usr/lib/mail/mail_pipe
                          mail_pipe program

   SEE ALSO
         mail(1), notify(1), vacation(1)








































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