$p
The sendmail process id All versions
The p
macro
contains the process ID of the
sendmail that executes the
delivery agent. Every process (running program)
under Unix has a unique identification number
associated with it (a process ID). Process IDs are
necessary to differentiate one incantation of a
program from another. The
sendmail program
fork(2)s often to perform
tasks (such as delivery) while performing other
tasks (such as listening for incoming SMTP
connections). All copies share the name
sendmail; each has a unique
process ID number.
$p
is intended for
use in header definitions but can also be used in
the A=
equate
(A= on page 738) of
delivery agents.
$p
is transient. If
it is defined in the configuration file or in the
command line, that definition can be ignored by
sendmail. Note that a
$&
prefix
is necessary when you reference this macro in rules
(that is, use $&p
, not $p
).
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