tcl script for ping not working - networking

Question

I have a tcl code which invokes ping command and returns its response , code is as follows
proc ping-igp {} {
foreach i {
127.0.0.1
200.200.200.1
} {
if { [regexp "0% loss" [eval exec "ping $i -n 1" ]]} { puts “$i”} else { puts “$i failed” }
}
}
But while executing it I get o/p as follows,
% proc ping-igp {} {
foreach i {
127.0.0.1
200.200.200.1
} {
if { [regexp "0% loss" [eval exec "ping $i -n 1" ]]} { puts "$i"} else { puts "
$i failed" }
}
}
% ping-igp
"127.0.0.1"
Pinging 200.200.200.1 with 32 bytes of data:
Request timed out.
Ping statistics for 200.200.200.1:
Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),
child process exited abnormally
%
I want to know when I'm unable to ping 200.200.200.1 why my code doesn't process else clause and give o/p " 200.200.200.1 failed " in end . I'm matching "0% loss"
Many Thanx.

Answer 1

You need to catch the exec call to ping, in case it returns an error. Here's your code modified to use catch.
proc ping-igp {} {
foreach i {
127.0.0.1
200.200.200.1
} {
if {[catch {exec ping $i -n 1} result]} { set result 0 }
if { [regexp "0% loss" $result]} { puts "$i"} else { puts "$i failed" }
}
}
Running it now gives:
% ping-igp
127.0.0.1
200.200.200.1 failed
%

Answer 2

Here is something I created for my own use: a ping proc for Tcl. It is not perfect, but works:
package require Tclx; # Needed for lassign and wait
# Pings a host and returns 0 if OK, non-zero otherwise
proc ping {host} {
# TODO: Use different command for Windows OS
set childPid [exec ping -c 1 $host > /dev/null 2>#1 &]
lassign [wait $childPid] pid howItEnded exitCode
return $exitCode
}
# Test the ping proc
set hostList {google.com 10.0.0.99 foo.bar}
foreach host $hostList {
set code [ping $host]
puts [format "%4d %s" $code $host]
}
Sample output:
$ tclsh ping_test.tcl
0 google.com
2 10.0.0.99
68 foo.bar

Answer 3

proc ping_device { router ip_address max_tries } {
set tries 0
while {$tries <= $max_tries} {
if {[catch {exec ping $ip_address -c 5} result]} {
puts "Ping command failed on Linux machine"
incr tries
if {$tries > $max_tries} {
ats_log -error "Giving up on ping"
return 0
}
continue
}
if {[regexp {([1-5]+) *[packets]? *received} $result - packets]} {
puts "Able to ping device: $router and\
successfully received $packets packets"
return 1
} else {
puts "Not Able to ping device: $router"
incr tries
}
}
puts "Giving up on ping, returning 0"
return 0
}