[[add information about expect's spawn command, pointers to its man page on http://www.tcl.tk/man/, etc.]]


spawn creates a session with a program or remote device that [Expect] can manage.  Spawned sessions can be automated using other Expect commands, such as expect, [interact] and exp_send.

The [man] page for spawn is actually part of the Expect man page http://www.tcl.tk/man/expect5.31/expect.1.html.


A very simple example - [ping] an ip address:



        #!/bin/sh
	# The next line is executed by /bin/sh, but not tcl \
	exec /homes/ashnoc01/noc/rbacon/tcl/ActiveTcl/bin/tclsh8.4 $0 ${1+"$@"}

	package require Expect

	spawn -noecho /usr/local/bin/nping -c 5 $argv
	log_user 0
	expect {
		"\r"	{
			puts -nonewline "$expect_out(buffer)"
			exp_continue
			}
		eof	{
			puts -nonewline "$expect_out(buffer)"
			}
		}
	puts "AutoPing finished\n"
	exit

Output:

  > AutoPing 62.188.74.130
  PING 62.188.74.130: 64 data bytes
  EchoReply from 62.188.74.130: len=64 ttl=242 seq=0 time=81.157 ms.
  EchoReply from 62.188.74.130: len=64 ttl=242 seq=1 time=80.768 ms.
  EchoReply from 62.188.74.130: len=64 ttl=242 seq=2 time=80.709 ms.
  EchoReply from 62.188.74.130: len=64 ttl=242 seq=3 time=80.915 ms.
  EchoReply from 62.188.74.130: len=64 ttl=242 seq=4 time=80.940 ms.

  ----62.188.74.130 PING Statistics----
  5 transmitted, 5 received, 0.00% packet loss.
  round-trip (ms) min/avg/max = 80.709/80.898/81.157
                var/sdev/skew/kurt = 0.030/0.174/0.323/1.311
  AutoPing finished

----

''[escargo] 20 Sep 2005'' - Let's see if I remember this correctly.
A frequently made mistake in [Expect] is to spawn a new process in a procedure,
and then not assign the returned process identifier to anything that gets it out
of the proc local scope.

Without the '''pid''' to pass to other Expect commands, they won't work as
intended.  It might also be possible to pass the ''wrong'' '''pid''' because
of the overwriting (or not overwriting) the ''spawn_id''.

-----

''[RJ] 21 Sep 2005'' - You remember correctly. An important point. An example of that:

  proc connect_server {server} {
      spawn -noecho rlogin $server
      set sid($server) $spawn_id
      return $sid($server)
  }

  set sid(myserver) [connect_server myserver.org]
  set sid(otherserver) [connect_server otherserver.org
  expect $sid(myserver) "%"
  exp_send "ls -l\r"
  expect $sid(otherserver) "%"
  exp_send $sid(otherserver) "ls -l\r"
  expect $sid(myserver) "%"
  set output_from_myserver $expect_out(buffer)
  expect $sid(otherserver) "%"
  set output_from_otherserver $expect_out(buffer)
    ....do stuff with the server output

Arrays of spawn_ids allow you to connect to multiple servers and hold those connections open indefinitely, switching at will.

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[Category Command] | 
[Category Expect]