Using the Tcl regular expression engine, scripts can filter specific information from show commands and present it in a custom format. The following is an example of filtering the show interfaces command output and creating a comma-separated list of BRI interfaces on the router:

tclsh
proc get_bri {} {
    set check ""
    set int_out [exec "show interfaces"]
    foreach int [regexp -all -line -inline "(^BRI\[0-9]/\[0-9])" $int_out] {
        if {![string equal $check $int]} {
            if {[info exists bri_out]} {
                append bri_out "," $int
             } else {
                 set bri_out $int
             }
             set check $int
        }
    }
    return $bri_out
}

The following Tcl script is useful for sending e-mail messages from a router.

##
## Place required comments here!!!
##
package provide sendmail 2.0
# Sendmail procedure for Support
namespace eval ::sendmail {
    namespace export initialize configure sendmessage sendfile
    array set ::sendmail::sendmail {
        smtphost    mailhub
        from        ""
        friendly    ""
    }
    proc configure {} {}
    proc initialize {smtphost from friendly} {
        variable sendmail
        if {[string length $smtphost]} then {
            set sendmail(smtphost) $smtphost 
        }
        if {[string length $from]} then {
            set sendmail(from) $from
        }
        if {[string length $friendly]} then {
            set sendmail(friendly) $friendly
        }
    }
    proc sendmessage {toList subject body {tcl_trace 0}} {
        variable sendmail
        set smtphost $sendmail(smtphost)
        set from $sendmail(from)
        set friendly $sendmail(friendly)
        if {$trace} then {
            puts stdout "Connecting to $smtphost:25"
        }
        set sockid [socket $smtphost 25]
## DEBUG
set status [catch {
        puts $sockid "HELO $smtphost"
        flush $sockid
        set result [gets $sockid]
        if {$trace} then {
            puts stdout "HELO $smtphost\n\t$result"
        }
        puts $sockid "MAIL From:<$from>"
        flush $sockid
        set result [gets $sockid]
        if {$trace} then {
            puts stdout "MAIL From:<$from>\n\t$result"
        }
        foreach to $toList {
            puts $sockid "RCPT To:<$to>"
            flush $sockid
        }
        set result [gets $sockid]
        if {$trace} then {
            puts stdout "RCPT To:<$to>\n\t$result"
        }
        puts  $sockid "DATA "
        flush $sockid
        set result [gets  $sockid]
        if {$trace} then {
            puts stdout "DATA \n\t$result"
        }
        puts  $sockid "From: $friendly <$from>"
        foreach to $toList {
            puts $sockid "To:<$to>"
        }
        puts  $sockid "Subject: $subject"
        puts  $sockid "\n"
        foreach line [split $body "\n"] {
            puts  $sockid " $line"
        }
        puts  $sockid "."
        puts  $sockid "QUIT"
        flush $sockid
        set result [gets  $sockid]
        if {$trace} then {
            puts stdout "QUIT\n\t$result"
        }
} result]
        catch {close $sockid }
        if {$status} then {
	      return -code error $result
        }
        return
    }
    proc sendfile {toList filename subject {tcl_trace 0}} {
        set fd [open $filename r]
        sendmessage $toList $subject [read $fd] $trace
        return
    }
}

Using the Tcl shell, Tcl commands can perform actions on MIBs. The following example shows how to set up the community access strings to permit access to SNMP. Public access is read-only, but private access is read-write. The following example shows how to retrieve a large section of a table at once using the snmp_getbulk Tcl command extension.

Two arguments, non-repeatersand max-repetitions, must be set when an snmp_getbulk command is issued. The non-repeaters argument specifies that the first N objects are to be retrieved with a simple snmp_getnext operation. The max-repetitions argument specifies that up to M snmp_getnext operations are to be attempted to retrieve the remaining objects.

In this example, three bindings--sysUpTime (1.3.6.1.2.1.1.2.0), ifDescr (1.3.6.1.2.1.2.2.1.2), and ifType (1.3.6.1.2.1.2.2.1.3)--are used. The total number of variable bindings requested is given by the formula N + (M * R), where N is the number of non-repeaters (in this example 1), M is the max-repetitions (in this example 5), and R is the number of request objects (in this case 2, ifDescr and ifType). Using the formula, 1 + (5 * 2) equals 11; and this is the total number of variable bindings that can be retrieved by this snmp_getbulk request command.

Sample results for the individual variables include a retrieved value of sysUpTime.0 being 1336090, where the unit is in milliseconds. The retrieved value of ifDescr.1 (the first interface description) is FastEthernet0/0, and the retrieved value of ifType.1 (the first interface type) is 6, which corresponds to the ethernetCsmacd type.

snmp-server community public RO
snmp-server community private RW
tclsh
  snmp_getbulk public 1 5 1.3.6.1.2.1.1.2.0  1.3.6.1.2.1.2.2.1.2  1.3.6.1.2.1.2.2.1.3
  {<obj oid='sysUpTime.0' val='1336090'/>}
  {<obj oid='ifDescr.1' val='FastEthernet0/0'/>}
  {<obj oid='ifType.1' val='6'/>}
  {<obj oid='ifDescr.2' val='FastEthernet1/0'/>}
  {<obj oid='ifType.2' val='6'/>}
  {<obj oid='ifDescr.3' val='Ethernet2/0'/>}
  {<obj oid='ifType.3' val='6'/>}
  {<obj oid='ifDescr.4' val='Ethernet2/1'/>}
  {<obj oid='ifType.4' val='6'/>}
  {<obj oid='ifDescr.5' val='Ethernet2/2'/>}
  {<obj oid='ifType.5' val='6'/>}

The following example shows how to retrieve the sysDescr.0, sysObjectID.0, sysUpTime.0, sysContact.0, sysName.0, and sysLocation.0 variables--in this example shown as system.1.0, system.2.0, system.3.0, system.4.0, system.5.0, and system.6.0--from the SNMP entity on the router using the snmp_getid Tcl command extension.

tclsh
 snmp_getid public
 {<obj oid='system.1.0' val='Cisco Internetwork Operating System Software 
 Cisco IOS XE(tm) 7200 Software (C7200-IK9S-M), Experimental Version 12.3(20030507:225511)
 [geotpi2itd1 124]
 Copyright (c) 1986-2003 by Cisco Systems, Inc.
 Compiled Wed 21-May-03 16:16 by engineer'/>} 
 {<obj oid='system.2.0' val='products.223'/>}
 {<obj oid='sysUpTime.0' val='6664317'/>} 
 {<obj oid='system.4.0' val='1-800-553-2447 - phone the TAC'/>}
 {<obj oid='system.5.0' val='c7200.myCompany.com'/>}
 {<obj oid='system.6.0' val='Bldg 24, San Jose, CA'/>}

The following example shows how to retrieve a set of individual variables from the SNMP entity on the router using the snmp_getnext Tcl command extension:

snmp_getnext public 1.3.6.1.2.1.1.1.0 1.3.6.1.2.1.1.2.0 
 {<obj oid='system.2.0' val='products.223'/>}
 {<obj oid='sysUpTime.0' val='6683320'/>}

The following example shows how to retrieve a set of individual variables from the SNMP entity on the router using the snmp_getone Tcl command extension:

snmp_getone public 1.3.6.1.2.1.1.1.0 1.3.6.1.2.1.1.2.0 
 {<obj oid='system.1.0' val='Cisco Internetwork Operating System Software 
 Cisco IOS XE(tm) 7200 Software (C7200-IK9S-M), Experimental Version 12.3(20030507:225511)
 [geotpi2itd1 124]
 Copyright (c) 1986-2003 by Cisco Systems, Inc.
 Compiled Wed 21-May-03 16:16 by engineer'/>} 
 {<obj oid='system.2.0' val='products.223'/>}

The following example shows how to change something in the configuration of the router using the snmp_setany Tcl command extension. In this example, the hostname of the router is changed to TCLSNMP-HOST.

tclsh
 snmp_setany private 1.3.6.1.2.1.1.5.0 -d TCLSNMP-HOST
 {<obj oid='system.5.0' val='TCLSNMP-HOST'/>}