Why does this Expect script fall through on failure?

MattFunke · 03-25-2008, 04:12 PM

Can anyone tell me why this script attempts to expect the second block if the first block fails?:

#!/usr/bin/expect

set timeout 20

spawn snmpwalk -v 2c -c public [lindex $argv 0] system

expect {
timeout {send_user "Timed out...\n"; exec ./checker snmpwalk[lindex $argv 0]#00 FAIL; exit}
-ex "SNMPv2-MIB::sysDescr.0 = STRING: Linux csi-dsp2-dualband 2.4.32 #1" {exec ./checker snmpwalk[lindex $argv 0]#00 PASS}
}

expect {
timeout {send_user "Timed out...\n"; exec ./checker snmpwalk[lindex $argv 0]#01 FAIL; exit}
-ex "SNMPv2-MIB::sysObjectID.0 = OID: NET-SNMP-MIB::netSnmpAgentOIDs.10" {exec ./checker snmpwalk[lindex $argv 0]#01 PASS}
}

Here's the error I get:

spawn snmpwalk -v 2c -c public 192.168.1.200 system
Timeout: No Response from 192.168.1.200
expect: spawn id exp4 not open
while executing
"expect -nobrace timeout {send_user "Timed out...\n"; exec ./checker snmpwalk[lindex $argv 0]#01 FAIL; exit} -ex {SNMPv2-MIB::sysObjectID.0 = OID: NET-..."
invoked from within
"expect {
timeout {send_user "Timed out...\n"; exec ./checker snmpwalk[lindex $argv 0]#01 FAIL; exit}
-ex "SNMPv2-MIB::sysObjectID.0 = OID: NET..."
(file "./exp_snmp" line 12)

It was my impression that "exit" exits even multi-threaded apps in Tcl. So why does the expect script simply skip to the next block?

Thanks in advance for any help you can lend.

jlinkels · 03-27-2008, 03:02 AM

It does not execute the second block because the application simply stops executing when a timeout occurs. In other words, it doesn't handle your timeout correctly and it terminates immediately.

Interesting way to call SNMP from TCL though. Didn't think about it, have problem calling SNMP from TCL. Yesterday I posted this question It never appeared to me to do it like you do.

For your problem, include this statement in your program at the beginning:

Code:

exp_internal 1

and I expect that you can see why timeout is not handled gracefully.

jlinkels