SNMP error reporting to stdout

Question

Why does net-snmp after "No Such Object available on this agent at this OID" errors exit with 0 and print the error message to STDOUT while other errors are printed to STDERR and have an exit status 1? Compare:

$ /usr/bin/snmpget -Oqv -v2c -cpublic localhost .1.3.6.1.2.1.2.1.0 2> /dev/null
No Such Object available on this agent at this OID
$ echo $?
0

A erroneous community string or IP-Address, however, is handled differently (e.g. "publi" instead of "public"):

$ /usr/bin/snmpget -Oqv -v2c -cpubli localhost .1.3.6.1.2.1.2.1.0 2>&1 > /dev/null
Timeout: No Response from localhost.
$ echo $?
1

This is really irritating as I'm trying to write a function that does some sanity checks to make sure that certain MIBs/OIDs are indeed available on the agent to be queried. I'd like to be able to do something like this (in a bash script):

snmp_sanity_checks() {
  ...
  if ! err=$($snmpcmd); then
    echo "ERROR: $err"
    exit $UNKNOWN
  fi
  ...
}

Does anybody know the reason for this and how I can "fix" it?

Thanks

As it turns out, "No Such Object available on this agent at this OID" is not considered to be an error per se but an exception (for all versions > 1). This also means that there's no simple check for whether a variable holds valid data or not, because `err` in the above example will not be empty if an exception occurs. Workaround: use snmp version 1 — user3040975, Dec 18 '13 at 15:24

score 1 · Answer 1 · answered Dec 26 '14 at 18:19

As another workaround, you can do this:

snmp_sanity_checks() {
  ...
  if ! err=$($snmpcmd); then
    echo "ERROR: $err"
    exit $UNKNOWN
  elif [[ $err == 'No Such Object'* ]]; then
    echo "ERROR: $err"
    exit $UNKNOWN
  fi
  ...
}

Or if you want to handle both situations the same way then this works too:

snmp_sanity_checks() {
  ...
  if ! err=$($snmpcmd) || [[ $err == 'No Such Object'* ]]; then
    echo "ERROR: $err"
    exit $UNKNOWN
  fi
  ...
}

SNMP error reporting to stdout

1 Answers1