#!/bin/sh
# the next line restarts using tclsh \
exec tclsh "$0" ${1+"$@"}

# <URL:http://starbase.neosoft.com/~claird/comp.lang.tcl/fmm.html#invocation>
#     explains the initial line noise.

########
#
#	This is a simple but handy utility for forwarding a conventional
#	     Unix mail spool.
#
#	'Twould be straightforward enough to rewrite this in Python,
#	     sh, Python, Rexx, ...  Tcl worked out for me.  Perl has,
#	     I believe, a module that knows how to disassemble mail
#	     spools.
#
########

# Cut the spool into segments which begin with "^From ..."; each of
#     these is a message, and can be fed directly into sendmail.

# Note that modern BSDs keep spools in /var/spool/mail/$old.
#      I won't bother for now to make this robust.

# If I can't assume sendmail, what *is* safe?

proc usage {} {
  puts "Usage:  'forward.tcl OLD_ACCOUNT NEW_ADDRESS'."
  puts "Examples:  'forward.tcl someone someone@newdomain.com'."
  puts "           'tclsh forward.tcl person newname'."
  puts "           'forward.tcl person person73@somewhere.org'."
  exit 1
}


if {2 != $argc} {
  usage
}

foreach {old new} $argv {}

set fp [open /usr/spool/mail/$old]

set message {}

while {![eof $fp]} {
  gets $fp line
  if [regexp {^From } $line] {
    if {{} != $message} {
      puts [exec sendmail $new << $message]
    }
    set message {}
  }
  append message "$line\n"
}
  # Thanks to Stefan Bertels for noticing the necessity of the
  #    following clause.  Without it, the last message is
  #    subject to loss.
if {{} != $message} {
  puts [exec sendmail $new << $message]
}   
close $fp