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Tcl/OTcl TutorialTcl/OTcl TutorialTcl/OTcl TutorialTcl/OTcl TutorialTcl/OTcl TutorialTcl/OTcl TutorialTcl/OTcl TutorialTcl/OTcl Tutorial

Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 1ed

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Outline• Tcl

– OverviewV i bl d D t T– Variables and Data Type

– Input/Output– Mathematics– Control Structure– Procedures

OT l• OTcl – Class, Inheritance, Members, and Syntax– An ExampleAn Example– Useful procedures

Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 2

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lTcl• An Interpreter: p

– Interpret instructions lines by lines

– No need for compilation• Core language for NS2• Core language for NS2• Strength: Simplicity


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Tcl• Program invocation

>> tclsh [<filename> [<args>] ]>> tclsh [<filename> [<args>] ]>> ns [<filename> [<args>] ]

– No input arg = Enter Tcl environment; Take– No input arg = Enter Tcl environment; Take command line by line

– <filename> = an input Tcl file name– <args> = input arguments separated by white

spaces

• In the file <filename>, – <args> is stored in the internal variable $argv<args> is stored in the internal variable $argv– To retrieve nth (={0,1,…}) input argument,

executel d $ $

Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008.

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Tcl: Simple ExampleTcl: Simple Example

• Convert temperature from Fahrenheit (Tf) to Celsius (Tc): ( f) ( c)– Tc = f(Tf) = [ (Tf -32) *5/9 ]

Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 5PPrepook: T. Iss

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Tcl: Simple ExampleTcl: Simple Example

• Convert temperature from Fahrenheit (Tf) to Celsius (Tc): ( f) ( c)– Tc = f(Tf) = [ (Tf -32) *5/9 ]


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Tcl: Variable and Data TypeTcl: Variable and Data Type

• Everything is String.# var.tcl

>> tclsh var.tcl( 10 + 15 )( 25 )

Quiz: $c stores ( 10 + 15 )


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Tcl: Variable and Data TypeTcl: Variable and Data Type

• Referencing value $– name = “name”– $name = the value stored in the variable whose

name is “name”

• set: Value assignment / Retrieval– set <name> <expr> set the value of $<name> to <expr>– $<name> set return the value stored in $<name>

• unset: Remove the value stored in a variable– unset <name> Remove the value stored in <name>


unset name Remove the value stored in name

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T l V i bl d D t TTcl: Variable and Data Type

• From the previous example, insertunset cputs $cp


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Tcl: Variable and Data Type• Bracketing

Tcl: Variable and Data Type• Bracketing

– {}: Interpret as it is– “”: Interpolate the expression Interpolate the express on– []: Do this first– (): Indexing

• From the previous example, insert


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Tcl: Variable and Data Type

V i bl i l b l b d f lt

Tcl: Variable and Data Type

• Variable is global by default• Arrayy

– Regular array - Associative array

• List = A collection of itemsList A collection of items• Example: a list “mylist” which contain

th it 1 2 d 3Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008.

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Tcl: Variable and Data Type• List Creation: Use either

– set mylist [1 2 3]y– set mylist “1 2 3”– set mylist {1 2 3}set mylist {1 2 3}

• Member retrieval: Retrieve the nth

( {0 1 }) b f h li(={0,1,…}) member of the listlindex $mylist <n>lindex $mylist n

“$Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008.

• Quiz: lindex “$mylist 1” returns ( 2 )12

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Tcl: Variable and Data Type• Member setting:

lset $mylist <n> <value>$ y• Group retrieval setting: Return a

list containing the nth to mth memberlist containing the nth to mth member of the list

lrange $mylist <n> <m>• List Appending:• List Appending:

lappend $mylist $anotherlist

Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 13den

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Outline• Tcl





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T l I t/O t tTcl: Input/OutputT l Ch l I f h id• Tcl Channel: Interface to the outside world (4 types)

1 S d d i di1. Standard input: stdin2. Standard output: stdout3. Standard error: stderr4. File channel {r,w,a, r+, w+, a+}

– To obtain the channelopen <filename> [<acc_type>]

– To close the fileclose <channel>


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Tcl: Input/Output• gets: Read from the channel

gets <channel> <var>gets <channel> <var>• puts: Write to the channel

puts [-nonewline] [<channel>] <string>• Example: Copy input.txt to output.txtExample opy nput.txt to output.txt

Wait for “end of line”end of line

Write to the output


Write to the output file (output.txt)

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T l M h iTcl: Mathematics

• expr: Tell Tcl that the following is a mathematical expressionmathematical expression.

– expr <operand1> <operator> <operand2>– expr <function>(<arg>)

• Example: E mp– Operator: expr $a + 3– Function: expr log10(10)


Function: expr log10(10)

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Tcl: Mathematics• Lists of operators:


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Tcl: MathematicsTcl Mathematics• Lists of functions:

– double returns a floating point– rand returns a random number in [0,1]– srand returns a random integer– wide returns an integer part– hypot returns


See http://www.tcl.tk/man/tcl8.5/TclCmd/mathfunc.htm19

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Outline• Tcl





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Tcl: Control StructureTcl: Control Structure• if/else/elseif


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Tcl: Control StructureTcl: Control Structure• switch


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Tcl: Control StructureTcl: Control Structure• while/for/foreach


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Tcl: ProceduresTcl: Procedures• Definition:

proc <proc_name> { <arg1> … <argn> } {<actions><actions>return <returned_value>

}

• Invocation:set myvar [ <proc name> <val1> <valn> ]set myvar [ <proc_name> <val1> … <valn> ]

Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 24d

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Outline• Tcl





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OTcl: Main Components• Object oriented version of Tcl

Class = Definition for a group of objects• Class = Definition for a group of objects• I.E., we can instantiate objects from a

classclass.• Class Characterization

M b i bl i t– Member variable = instvars– Member procedure = instprocs

I h it• Inheritance– Base class = Mother class = Parent class

D i d cl ss child cl ss


– Derived class = child class

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Tcl

OT l S tOTcl: Syntax• Class Declaration

Class <classname> [-superclass <Baseclassname>][ p ]

• Instvar declaration: Declared in an instproc$self instvar <name1> <name2> …

• Instvar access: set– Retrieve the value:

$<object> set <instvar name>$<object> set <instvar_name>– Set the value:

$<object> set <instvar_name> <value>


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OTcl: SyntaxOTcl: Syntax• Instproc declaration

<classname> instproc <proc_name> {<arg1> <argn>} {{<arg1> … <argn>} {

<body>}

• Note: <argi> can be replace with { <argi>• Note: <argi> can be replace with { <argi> <def> }, where <def> is the default

l t ti ll i d if thvalue, automatically assigned if the value is not specified at the invocation.


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OTcl: SyntaxOTcl: Syntax

• Instproc invocation<object> <proc name> <val1> <valn><object> <proc_name> <val1> … <valn>

• Object construction– Basic: <classname> <object_name>– NS2: new <classname>NS2: new classname

• new does two thingsll { } ll– alloc{…}: Allocate memory

– init{…}: Necessary initialization


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Outline• Tcl





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OTcl: ExampleOTcl: Example• Base Class = Class NodeBase Class Class Node

– Instvar = stateI st ( )– Instproc = recv(…)

• Derived Class = Class Mobile– Derive all instvars and instprocs from

class Nodeclass Node– Instvar = location

Instproc = move( )– Instproc = move(…)

Textbook: T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer 2008. 31dc =

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OTcl: ExampleBASE CLASS pClass Node

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OTcl: ExampleOTcl Example• Constructor

• InvocationObject instantiationObject instantiation

R t th

Set the instvar

Return the value stored in the instvar Invoke the


“state” to be 0 “state”Invoke the instproc “move”

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OT l U f l P dOTcl: Useful Procedures• next: Invoke the instproc (with the same name) of n t n o th nstproc (w th th sam nam ) of

the base class.$self next [<args>][ g ]

• info: Return the information of – Instvar: <varname> info <options>


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OT l U f l P dOTcl: Useful Proceduresi f R h i f i f• info: Return the information of – Class: <classname> info <options>


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OT l U f l P dOTcl: Useful Procedures• More on procedure pertaining to

– Class: Visitftp://ftp.tns.lcs.mit.edu/pub/otcl/doc/class.html

– Object: Visitftp://ftp tns lcs mit edu/pub/otcl/doc/object htmlftp://ftp.tns.lcs.mit.edu/pub/otcl/doc/object.html


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Summary• Tcl





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