topic Re: adding elements to an array in Operating System - Linux

adding elements to an array

Chris Vidal — Thu, 13 Jul 2006 16:55:39 GMT

snmpwalk -c xx yy system generates the following.

cvidal@cayd04-mds1:~> snmpwalk -c tmedomain4 192.168.63.247 system
sysDescr.0 = STRING: Cisco IOS Software, 3800 Software (C3845-ADVIPSERVICESK9-M), Version 12.4(3b), RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2005 by Cisco Systems, Inc.
Compiled Fri 09-Dec-05 09:08 by alnguyen
sysObjectID.0 = OID: enterprises.9.1.544
sysUpTime.0 = Timeticks: (28557767) 3 days, 7:19:37.67
sysContact.0 = STRING: MCI 800-256-9284
sysName.0 = STRING: merv-m008napa-687103
sysLocation.0 = STRING:
sysServices.0 = INTEGER: 78
sysORLastChange.0 = Timeticks: (0) 0:00:00.00

I would like to put each line into an array element as I receive the response for later printing or assigning to vars

set -A ARRAY just setsup a single element array.

tks

Re: adding elements to an array

Sandman! — Thu, 13 Jul 2006 17:19:03 GMT

>I would like to put each line into an array element as I receive the response for >later printing or assigning to vars

# snmpwalk -c xx yy system | awk '{l[NR]=$0}'

Re: adding elements to an array

A. Clay Stephenson — Thu, 13 Jul 2006 17:30:35 GMT

Here's a simple example using the output of ls -l /tmp but it should give you the idea:

#!/usr/bin/sh

typeset PROG=${0}
typeset -i MAXARRAY=1023
typeset -i KNT=0
typeset X=""
typeset -i STAT=0

#your snmpwalk will replace the ls -l

ls -l /tmp | while read X
do
typeset A[${KNT}]="${X}"
((KNT += 1))
if [[ ${KNT} -gt ${MAXARRAY} ]]
then
STAT=255
echo "${PROG}: Missing elements" >&2
break
fi
done
# Now let's read 'em out
typeset -i I=0
while [[ ${I} -lt ${KNT} ]]
do
echo "${I} -> \"${A[${I}]}\""
((I += 1))
done
exit ${STAT}

----------------------------

Note that shell arrays are limited to a maximum of 1024 elements so you might want to rethink your problem (Perl?).

Re: adding elements to an array

Ralph Grothe — Fri, 14 Jul 2006 02:18:19 GMT

You could maybe try something like

typeset -i i=-1; set -A SNMPWALK
/your/snmpwalk_cmd 2>/dev/null \
| while read line; do
SNMPWALK[$((i+=1))]="$line"
done

But beware not to start your snmpwalk too high in the tree because afaik a shell array can only hold up to 1024 elements.
Besides, because of wasteful memory usage
dumping large amounts of output in arrays is not considered terribly efficient programming.

In Perl it is much easier to store each output line as an array element,
and there you are only restricted by your process'es memory share.
But for efficiency's sake one shouldn't store it in an array.

e.g.

my @SNMPWALK = qx(/your/snmpwalk_cmd);

or if you want more control

local *SNMP_PIPE
my $child = open SNMP_PIPE, '-|';
die "Cannot open pipe to snmpwalk" if !defined $child;
if ($child) {
@SNMPWALK = ;
close SNMP_PIPE;
} else {
local %ENV; # if taint mode demands
exec qw(/path/to/snmpwalk arg1 arg2 arg3);
}
# maybe you want to chomp new lines
chomp @SNMPWALK

Re: adding elements to an array

Chris Vidal — Fri, 14 Jul 2006 11:46:46 GMT

Done