AWk SCRIPTING ON NS2 WITH SCRIPTS

AWK Script

AWK is a high level programming language which is used to process text files,named after its three orginal author's name:

A  : Alfred Aho

W : Peter Weinberger

K  : Brian Kernighan 

AWK Scripts are very good in processing the data from the log (trace files) which we get from NS2. If you want to process the trace file manually.

AWK PROGRAM STRUCTURE

Awk program structure contains mainly three parts;

1. Begin

2. Content

3. End

BEGIN {<initialization>}

   <pattern1> {<actionSet1>}

   <pattern2> {<actionSet2>}

   . . .

END {<final finalActionSet>}

BEGIN : Begin deals with what to be executed prior to text file processing,normally which is used to initialize variable values or constants.

CONTENT : Script which process the text file. In this part, AWK moves lines by lines (i.e., records by records) and executes the <actionSet> if the current line match with the pattern. The actions repeats until AWK reaches the end of the file. 

END : This part explains what to be executed after the text file processing ie. what to print on the terminal or to show output in terminal.

EXECUTION

Awk has two types of execution;

1) Plain Execution.

2) Match and Execute.

Plain Execution : Simply AWK statements.

Match and execute : The second type of execution is “Match and Execute”, when executes plain execution statements only if the current line (of the input text file) matches with a predefined pattern. The pattern can be either : 1. Logical Expression 2. Regular Expression.

Sample Awk Script

TRACE FILE AND AWK SCRIPT

Here is a sample of trace file from NS2 , to know more about trace file click here

AWK Scripts are very good in processing the data column wise. For example the first column in the above trace file represents r, s which indicates receive, sent respectively. If we want to trace the entire r and s alone from this trace file we can represent it as $1

So

$1 : Action (r,s,d.f)

$2 Time

$3 Time value

$4 node id

$5 node id value

$6 id of next hop

$7 next hop id value

.

.

.

. 

More description of trace file is in above link.

To run awk script, we have to use terminal window.

For that first we have to install gawk in Linux.for that we have to write following code in terminal;

sudo apt-get install gawk

after installing gawk, we have to  run the awk script using command; 

gawk -f <awk file name> <trace file name> 

gawk -f file.awk file.tr

The ‘-f’ instructs the awk utility to get the awk program from the source file i.e from .awk file.

After entering command you will get values.