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Table Of Contents
Prerequisites for Cisco IOS Scripting with Tcl
Restrictions for Cisco IOS Scripting with Tcl
Information About Cisco IOS Scripting with Tcl
Tcl Shell for Cisco IOS Software
How to Configure Cisco IOS Scripting with Tcl
Enabling the Tcl Shell and Using the CLI to Enter Commands
Custom Extensions in the Tcl Shell
Using the Tcl Shell to Access SNMP MIB Objects
SNMP MIB Custom Extensions in the Tcl Shell
Running Predefined Tcl Scripts
Configuration Examples for Cisco IOS Scripting with Tcl
Tcl Script Using the show interfaces Command: Example
Tcl Script for SMTP Support: Example
Tcl Script for SNMP MIB Access: Examples
Feature Information for Cisco IOS Scripting with Tcl
Cisco IOS Scripting with Tcl
First Published: July 28, 2003Last Updated: May 19, 2008The Cisco IOS Scripting with Tcl feature provides the ability to run Tool Command Language (Tcl) version 8.3.4 commands from the Cisco IOS command-line interface (CLI).
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for Cisco IOS Scripting with Tcl" section.
Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for Cisco IOS Scripting with Tcl
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Prerequisites for Cisco IOS Scripting with Tcl
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Restrictions for Cisco IOS Scripting with Tcl
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Caution
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Information About Cisco IOS Scripting with Tcl
To create and use Tcl scripts within Cisco IOS software, you should understand the following concepts:
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Tcl Shell for Cisco IOS Software
The Cisco IOS Tcl shell was designed to allow customers to run Tcl commands directly from the Cisco IOS CLI prompt. Cisco IOS software does contain some subsystems such as Embedded Syslog Manager (ESM) and Interactive Voice Response (IVR) that use Tcl interpreters as part of their implementation. These subsystems have their own proprietary commands and keyword options that are not available in the Tcl shell.
Several methods have been developed for creating and running Tcl scripts within Cisco IOS software. A Tcl shell can be enabled, and Tcl commands can be entered line by line. After Tcl commands are entered, they are sent to a Tcl interpreter. If the commands are recognized as valid Tcl commands, the commands are executed and the results are sent to the tty. If a command is not a recognized Tcl command, it is sent to the Cisco IOS CLI parser. If the command is not a Tcl or Cisco IOS command, two error messages are displayed. A predefined Tcl script can be created outside of Cisco IOS software, transferred to flash or disk memory, and run within Cisco IOS software. It is also possible to create a Tcl script and precompile the code before running it under Cisco IOS software.
Multiple users on the same router can be in Tcl configuration mode at the same time without interference because each Tcl shell session launches a separate interpreter and Tcl server process. The tty interface number served by each Tcl process is represented in the server process name and can be displayed using the show process CLI command.
The Tcl shell can be used to run Cisco IOS CLI EXEC commands within a Tcl script. Using the Tcl shell to run CLI commands allows customers to build menus to guide novice users through tasks, to automate repetitive tasks, and to create custom output for show commands.
Tcl Precompiler
The Cisco IOS Tcl implementation offers support for loading scripts that have been precompiled by the TclPro precompiler. Precompiled scripts allow a measure of security and consistency because they are obfuscated.
SNMP MIB Object Access
Designed to make access to Simple Network Management Protocol (SNMP) MIB objects easier, a set of UNIX-like SNMP commands has been created. The Tcl shell is enabled either manually or by using a Tcl script, and the new commands can be entered to allow you to perform specified get and set actions on MIB objects. To increase usability, the new commands have names similar to those used for UNIX SNMP access. To access the SNMP commands go to, "Using the Tcl Shell to Access SNMP MIB Objects" section.
How to Configure Cisco IOS Scripting with Tcl
This section contains the following tasks:
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Enabling the Tcl Shell and Using the CLI to Enter Commands
Perform this task to enable the interactive Tcl shell and to enter Tcl commands line by line through the Cisco IOS CLI prompt. Optional steps include specifying a default location for encoding files and specifying an initialization script.
Custom Extensions in the Tcl Shell
The Cisco IOS implementation of the Tcl shell contains some custom command extensions. These extensions operate only under Tcl configuration mode. Table 2 displays these command extensions.
SUMMARY STEPS
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DETAILED STEPS
Step 1
enable
Example:Router> enable
Enables privileged EXEC mode.
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Step 2
configure terminal
Example:Router# configure terminal
(Optional) Enters global configuration mode.
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Step 3
scripting tcl encdir location-url
Example:Router(config)# scripting tcl encdir tftp://10.18.117.23/enctcl/
(Optional) Specifies the default location of external encoding files used by the Tcl encoding command.
Step 4
scripting tcl init init-url
Example:Router(config)# scripting tcl init ftp://user:password@172.17.40.3/tclscript/initf iles3.tcl
(Optional) Specifies an initialization script to run when the Tcl shell is enabled.
Step 5
scripting tcl low-memory bytes
Example:Router(config)# scripting tcl low-memory 33117513
(Optional) Specifies a low water memory mark for free memory for Tcl-based applications. The memory threshold can be set anywhere between 0-4294967295 bytes.
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Step 6
exit
Example:Router(config)# exit
(Optional) Exits global configuration mode and returns to privileged EXEC mode.
Step 7
tclsh
Example:Router# tclsh
Enables the interactive Tcl shell and enters Tcl configuration mode.
Step 8
Enter the required Tcl command language syntax.
Example:Router(tcl)# proc get_bri {}
Commands entered in Tcl configuration mode are sent first to the interactive Tcl interpreter. If the command is not a valid Tcl command, it is then sent to the CLI parser.
Step 9
ios_config "cmd" "cmd-option"
Example:Router(tcl)# ios_config "interface Ethernet 2/0" "no keepalive"
(Optional) Modifies the router configuration using a Tcl script by specifying the Tcl command ios_config with CLI commands and options. All arguments and submode commands must be entered on the same line as the CLI configuration command.
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Step 10
exec "exec-cmd"
Example:Router(tcl)# exec "show interfaces"
(Optional) Executes Cisco IOS CLI EXEC mode commands from a Tcl script by specifying the Tcl command exec with the CLI commands.
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Step 11
exit
Example:Router(tcl)# exit
Exits Tcl configuration mode and returns to privileged EXEC mode.
Examples
The following sample partial output shows information about Ethernet interface 0 on the router. The show interfaces command has been executed from Tcl configuration mode.
Router# tclshRouter(tcl)# exec "show interfaces"Ethernet 0 is up, line protocol is upHardware is MCI Ethernet, address is 0000.0c00.750c (bia 0000.0c00.750c)Internet address is 10.108.28.8, subnet mask is 255.255.255.0MTU 1500 bytes, BW 10000 Kbit, DLY 100000 usec, rely 255/255, load 1/255Encapsulation ARPA, loopback not set, keepalive set (10 sec)ARP type: ARPA, ARP Timeout 4:00:00Last input 0:00:00, output 0:00:00, output hang neverLast clearing of "show interface" counters 0:00:00Output queue 0/40, 0 drops; input queue 0/75, 0 dropsFive minute input rate 0 bits/sec, 0 packets/secFive minute output rate 2000 bits/sec, 4 packets/sec1127576 packets input, 447251251 bytes, 0 no bufferReceived 354125 broadcasts, 0 runts, 0 giants, 57186* throttles0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort5332142 packets output, 496316039 bytes, 0 underruns0 output errors, 432 collisions, 0 interface resets, 0 restarts...Troubleshooting Tips
Use the Tcl puts command in a Tcl script to trace command execution.
Using the Tcl Shell to Access SNMP MIB Objects
Perform this optional task to enable the interactive Tcl shell and enter Tcl commands to perform actions on MIB objects.
SNMP MIB Custom Extensions in the Tcl Shell
The Cisco IOS implementation of the Tcl shell contains some custom command extensions for SNMP MIB object access. These extensions operate only under Tcl configuration mode. Table 3 displays these command extensions.
Prerequisites
The SNMP community configuration must exist in the running configuration of the router.
SUMMARY STEPS
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DETAILED STEPS
Step 1
enable
Example:Router> enable
Enables privileged EXEC mode.
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Step 2
configure terminal
Example:Router# configure terminal
(Optional) Enters global configuration mode.
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Step 3
scripting tcl encdir location-url
Example:Router(config)# scripting tcl encdir tftp://10.18.117.23/enctcl/
(Optional) Specifies the default location of external encoding files used by the Tcl encoding command.
Step 4
scripting tcl init init-url
Example:Router(config)# scripting tcl init ftp://user:password@172.17.40.3/tclscript/initf iles3.tcl
(Optional) Specifies an initialization script to run when the Tcl shell is enabled.
Step 5
exit
Example:Router(config)# exit
(Optional) Exits global configuration mode and returns to privileged EXEC mode.
Step 6
tclsh
Example:Router# tclsh
Enables the interactive Tcl shell and enters Tcl configuration mode.
Step 7
Enter the required Tcl command language syntax.
Example:Router(tcl)# proc get_bri {}
Commands entered in Tcl configuration mode are sent first to the interactive Tcl interpreter. If the command is not a valid Tcl command, it is sent to the CLI parser.
Step 8
snmp_getbulk community-string non-repeaters max-repetitions oid [oid2 oid3...]
Example:Router(tcl)# snmp_getbulk public 1 3 1.3.6.1.2.1.1.1 1.3.6.1.2.1.10.18.8.1.1
(Optional) Retrieves a large section of a MIB table.
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Step 9
snmp_getid community-string
Example:Router(tcl)# snmp_getid private
(Optional) Retrieves the following variables from the SNMP entity on the router: sysDesrc.0, sysObjectID.0, sysUpTime.0, sysContact.0, sysName.0, and sysLocation.0.
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Step 10
snmp_getnext community-string oid [oid2 oid3...]
Example:Router(tcl)# snmp_getnext public 1.3.6.1.2.1.1.1.0 1.3.6.1.2.1.1.2.0
(Optional) Retrieves a set of individual variables from a MIB table.
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Step 11
snmp_getone community-string oid [oid2 oid3...]
Example:Router(tcl)# snmp_getone public 1.3.6.1.2.1.1.1.0 1.3.6.1.2.1.1.2.0
(Optional) Retrieves a set of individual variables from a MIB table.
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Step 12
snmp_setany community-string oid type val [oid2 type2 val2...]
Example:Router(tcl)# snmp_setany private 1.3.6.1.2.1.1.5.0 -d TCL-SNMP_TEST
(Optional) Retrieves current values of specified variables from a MIB table and then performs a set request on the variables.
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Step 13
exit
Example:Router(tcl)# exit
Exits Tcl configuration mode and returns to privileged EXEC mode.
Troubleshooting Tips
Use the Tcl puts command in a Tcl script to trace command execution.
Running Predefined Tcl Scripts
Perform this optional task to run a predefined Tcl script in Cisco IOS software.
Prerequisites
Before performing this task, you must create a Tcl script that can run on Cisco IOS software. The Tcl script may be transferred to internal flash memory using any file system that the Cisco IOS file system (IFS) supports, including TFTP, FTP, and rcp. The Tcl script may also be sourced from a remote location.
SUMMARY STEPS
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DETAILED STEPS
Configuration Examples for Cisco IOS Scripting with Tcl
This section provides the following configuration examples:
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Tcl Script Using the show interfaces Command: Example
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:
tclshproc 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}Tcl Script for SMTP Support: Example
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 Supportnamespace eval ::sendmail {namespace export initialize configure sendmessage sendfilearray set ::sendmail::sendmail {smtphost mailhubfrom ""friendly ""}proc configure {} {}proc initialize {smtphost from friendly} {variable sendmailif {[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 sendmailset 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]## DEBUGset status [catch {puts $sockid "HELO $smtphost"flush $sockidset result [gets $sockid]if {$trace} then {puts stdout "HELO $smtphost\n\t$result"}puts $sockid "MAIL From:<$from>"flush $sockidset 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 $sockidset 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 $sockidset 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] $tracereturn}}Tcl Script for SNMP MIB Access: Examples
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-repeaters and 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 ROsnmp-server community private RWtclshsnmp_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.
tclshsnmp_getid public{<obj oid='system.1.0' val='Cisco Internetwork Operating System SoftwareCisco IOS(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 SoftwareCisco IOS(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.
tclshsnmp_setany private 1.3.6.1.2.1.1.5.0 -d TCLSNMP-HOST{<obj oid='system.5.0' val='TCLSNMP-HOST'/>}Additional References
The following sections provide references related to the Cisco IOS Scripting with Tcl feature.
Related Documents
Embedded Syslog Manager
Embedded Syslog Manager module
Network Management commands (including Tcl and logging commands): complete command syntax, defaults, command mode, command history, usage guidelines, and examples
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
RFCs
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
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Technical Assistance
Command Reference
The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Network Management Command Reference at http://www.cisco.com/en/US/docs/ios/netmgmt/command/reference/nm_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.
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Feature Information for Cisco IOS Scripting with Tcl
Table 4 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Glossary
ESM—Embedded Syslog Manager.
IVR—Interactive Voice Response.
MIB—Management Information Base.
SNMP—Simple Network Management Protocol.
Tcl—Tool Command Language.
Note
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