Computer Networking
Lab-03
Learning TCL
Convention: TCL commands are shown in italic
Warm Up
If you have practiced the last lab sufficiently you may skip the warm up
Open working console
Start cygwin (for installation problem read and re-install the ns2 using the installation guide)
Start xserver by typing startxwin.bat
Minimize the bash console and work in the new window opened by startxwin.bat
Basic Commands Examples
puts string puts HelloWorld
puts “sentence or word or letter or variable or expression ” puts “Hello World”
puts {sentence or word or letter or variable or expression} puts {Hello world }
set variable_name variable_value set num 10
set variable_name [expression] set sum [expr 10+20]
set variable_name $variable_value set num2 $num1
New Lessons
Lesson – 01 Writing TCL commands in a file and executing
Command: source filename
TCL commands can be written in a file and the file can be executed using the interpreter through source command,
the source command takes a file name as argument, if the file path is not already set using environment variable
PATH, one has to provide full path name, if path is already defined one has to provide only the file name with
extension.
Example:
1- Create a file temp.txt in your /home/DCIS directory
2- iin the file write puts “Hello World” and save the file
3- go to tcl interpreter prompt and write source temp.txt
4- result : command prompt should display “Hello World”
Exercise-01
Write tcl code that displays your bio data as student of BS CIS i.e. your name, batch, subject etc.
Exercise-01 (use file)
Write a program that adds two numeric values by using a procedure, for that you have to define the following at least
1- A procedure (choose a suitable for that)
2- Create three variables, assign values one of them should have a value = 0
3- Display the values of the variables
4- Display a sentence “Calling Procedure
5- Use the procedure and store the value in third variable with value = 0
6- Display the value of the third variable
The output should look like
The variables are
A = 10 , B = 20 Result = 0
Calling the procedure “sum”
A + B = 30
Lesson – 02 User Input
Command: gets stdin
gets reads data from a given input stream , an input stream is any source of data , it can be a file or can be direct
user input from command line, stdin is standard input stream i.e. read from console, so to read from console the
command will be gets stdin, the gets command is used like expr comamnd
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