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Checking network continuity using ping, Expect and a Tk GUI
Expect Processes example from a Well House Consultants training course
More on Expect Processes [link]

This example is described in the following article(s):
   • Parallel Pinging, using Python Threads or Expect spawn lists - [link]
   • Checking all the systems on a subnet, using Expect and Tk - [link]

Source code: tkpingle Module: T212
#!/usr/bin/env expectk

# check a number of systems for signs of life at the same time
# expect + tk - checking multiple hosts graphically by ping

if {[llength $argv] < 1} {
        set argv {bhuna samosa balti madras ceylon curry dhansak
        vindaloo nan pillau chapatti dupiaza otter seal whale saturn panther}

set high [expr [llength $argv] * 32 + 64]
wm geometry . 200x$high
foreach system $argv {
        label .la_$system -text $system
        pack .la_$system -fill both -expand true -padx 5 -pady 5
. config -background white
button .quit -text quit -command exit
button .redo -text "Run tests" -command {

log_user 0
set timeout 60
set runningcount 0

# spawn out a series of pings

foreach system $argv {
        spawn ping -c 3 $system
        set id($system) $spawn_id
        set backlook($spawn_id) $system
        set good($system) 0
        lappend idlist $id($system)
        .la_$system config -background red
        incr runningcount

# gather up a series of responses

while {$runningcount > 0} {

expect {
        -i $idlist "\n" {
                set which $expect_out(spawn_id)
                lappend ans($which) $expect_out(buffer)
                set system $backlook($which)
                if {[regexp "^64 " $expect_out(buffer)]} {
                        incr good($system)
                        set newcol [lindex {red orange yellow green} $good($system)]
                        .la_$system config -background $newcol
        eof {
                # search and remove completed host from idlist
                set donepos [lsearch $idlist $expect_out(spawn_id)]
                set idlist [lreplace $idlist $donepos $donepos]
                incr runningcount -1
        timeout {


pack .redo .quit -fill both -expand true -padx 5 -pady 5

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to program in Tcl
 * Tcl Programming
 * Tcl Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Tcl, Tk and Expect are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Expect Processes" training module. You'll find a description of the topic and some other closely related examples on the "Expect Processes" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

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