#
# GETNEXT Command Generator Application
#
# Perform SNMP GETNEXT operation with the following options:
#
# with SNMPv1, community 'public'
# over IPv4/UDP
# to an Agent at demo.snmplabs.com:161
# two columns of the IF-MIB::ifEntry table
# search for pysnmp MIBs at specific filesystem location
# stop when response OIDs leave the scopes of initial OIDs
#
# This script performs similar to the following Net-SNMP command:
#
# $ snmpwalk -v1 -c public -ObentU demo.snmplabs.com IF-MIB::ifDescr IF-MIB::ifType
#
# The pysnmp engine maintains its own MIB search path which is usued
# for searching for MIB modules by name. By default pysnmp will search
# its built-in MIB repository (pysnmp.smi.mibs.instances, pysnmp.smi.mibs)
# and pysnmp-mibs package (pysnmp_mibs). Those two entries are normally
# found relative to $PYTHONPATH. Besides searching MIBs as Python modules
# (which could be egg-ed or not), pysnmp can also search for stand-alone
# files in given directories. The latter could be specified by 
# ObjectIdentity.addMibSource() calls. New search path entries are added
# in front of existing ones in search path.
#
from pysnmp.entity.rfc3413.oneliner.cmdgen import *

for errorIndication, \
    errorStatus, errorIndex, \
    varBinds in nextCmd(SnmpEngine(),
                        CommunityData('public', mpModel=0),
                        UdpTransportTarget(('demo.snmplabs.com', 161)),
                        ContextData(),
                        ObjectType(ObjectIdentity('IF-MIB', 'ifDescr').addMibSource('/tmp/mymibs')),
                        ObjectType(ObjectIdentity('IF-MIB', 'ifType')),
                        lookupNames=True, lookupValues=True):
    # Check for errors and print out results
    if errorIndication:
        print(errorIndication)
        break
    else:
        if errorStatus:
            print('%s at %s' % (
                    errorStatus.prettyPrint(),
                    errorIndex and varBinds[int(errorIndex)-1][0] or '?'
                )
            )
            break
        else:
            for varBind in varBinds:
                print(' = '.join([ x.prettyPrint() for x in varBind ]))