sendmail, 4th Edition

P=

Path to the delivery agent All versions

The P= delivery agent equate specifies the full pathname of the program that will act as the delivery agent. The form for the P= delivery agent equate looks like this:

P=path

If path is missing, sendmail will print the following error message and set P= to NULL:

mailer agent_name: empty pathname

The path can also be one of three names that are defined internally to sendmail. Those internally defined names are [IPC], which tells sendmail to forward mail over a kernel-supported (usually TCP/IP) network; [FILE], which tells sendmail to deliver to a file; and [LPC], which is used for debugging.

P=path

When the path begins with a slash character (when it is a full pathname), sendmail first forks (creates a copy of itself), and then the child process (the copy) execs (replaces itself with) the program. The argument vector (argv, or command-line arguments) supplied to the program is specified by the A= delivery agent equate (A= on page 738). The program inherits the environment^[280] of sendmail and has its standard input and output connected to the parent process (the sendmail that forked). The message (header and body) is fed to the program through its standard input. The envelope (sender and recipient addresses) might or might not be provided on the command line, depending on the nature of the program as defined by its F= delivery agent flags. If A= does not include the $u sendmail macro, sendmail will speak SMTP, or LMTP if the delivery agent has ...