show cdp neighbor in expect script - regex

Question

I'm pretty new to scripting in general. I'm writing an expect script that ssh'es into a Cisco switch, and runs the "show cdp neighbors" command to get a list of all the devices connected to the switch. I then save the output into a variable and exit the ssh session.
I have the username and password being set in the included file.
#!/usr/bin/expect -f
#exp_internal 1
source accountfile
set timeout 10
spawn $env(SHELL)
expect "#"
send "ssh $USERNAME#<hostname>\r"
expect {
"continue connecting" {
send_user "Adding host to ssh known hosts list...\n"
send "yes\n"
exp_continue
}
"Do you want to change the host key on disk" {
send_user "Changing host key on disk...\n"
send "yes\n"
exp_continue
}
"assword:" {
send "$PASSWORD\r"
}
}
expect "#"
send "term len 0\r"
expect "#"
send "show cdp neighbors\r"
expect "#"
set result $expect_out(buffer)
send "exit\r"
expect "#"
So then I want to take $result and look for lines that contain ' R ', and save those lines to a file (R with spaces on either side indicates a router, which is what I'm interested in)
The problem is that if the name of a connected device is long, it puts the name of the device on one line, and then the rest of the data about the device on the next line. So if I match the ' R ' string, I won't get the name of the device, since the name is on the previous line.
Device ID Local Intrfce Holdtme Capability Platform Port ID
...
<device_name_really_long>
Gig 2/0/52 171 R S I WS-C6509 Gig 3/14
<device_name2> Gig 2/0/1 131 H P M IP Phone Port 1
...
Any ideas? there's probably a regex that would do it, but I don't know squat about regex.
SOLVED: thanks to Glenn Jackman
I ended up having to add an expect condition to check if I had a full buffer, so my final code looks like this:
#!/usr/bin/expect
#exp_internal 1
match_max 10000
set expect_out(buffer) {}
set timeout 30
source accountfile
spawn $env(SHELL)
expect "#"
send "ssh $USERNAME#ol2110-3750stack.sw.network.local\r"
expect {
"continue connecting" {
send_user "Adding host to ssh known hosts list...\n"
send "yes\n"
exp_continue
}
"Do you want to change the host key on disk" {
send_user "Changing host key on disk...\n"
send "yes\n"
exp_continue
}
"assword:" {
send "$PASSWORD\r"
}
}
expect "#"
send "term len 0\r"
expect "#"
send "show cdp neighbors\r"
set result ""
expect {
{full_buffer} {
puts "====== FULL BUFFER ======"
append result $expect_out(buffer)
exp_continue
}
"#" {
append result $expect_out(buffer)
}
}
send "exit\r"
expect "#"
set devices [list]
set current_device ""
set lines [split $result "\n"]
foreach line $lines {
set line [string trim $line]
if {[llength $line] == 1} {
set current_device $line
continue
}
set line "$current_device$line\n"
if {[string match {* R *} $line]} {
lappend devices $line
}
set current_device ""
}
puts $devices

Answer 1

set devices [list]
set current_device ""
foreach line [split $result \n] {
if {[llength [split [string trim $line]]] == 1} {
set current_device $line
continue
}
set line "$current_device$line"
if {[string match {* R *} $line]} {
lappend devices $line
}
set current_device ""
}
# devices list should now contain "joined" routers.