Reading Trace file from NS2 using gawk

Question

I am new user of gawk. I am trying to read trace file by putting a small code in a file and then by making that file executable. Following is what I am trying to do.

#!/bin/sh 
set i = 0 
while ($i < 5) 
awk 'int($2)=='$i' && $1=="r"  && $4==0 {pkt += $6} END {print '$i'":"pkt}'  out.tr 
set i = `expr $i + 1` 
end

after this I am running following command:

sh ./test.sh

and it says:

syntax error: word unexpected (expecting do)

any help?

Answer 1

Assuming you are using bash

Syntax of while loop:

while test-commands; do consequent-commands; done

more info

For comparison using < operator you need to use Double-Parentheses see Shell Arithmetic and Conditional Constructs.

To assign value to the variable you used in the code just write i=0.

To access a shell variable in awk use -v option of awk.

Thus your might be become like this:

i=0 
while ((i < 5))
do
  awk -v k=$i 'int($2)==k && $1=="r"  && $4==0 {pkt += $6} END {print k":"pkt}'  out.tr 
  i=`expr $i + 1`
done

Here the variable k in awk code, has the value of variable $i from shell. Instead of expr $i + 1 you can use $((i + 1)) or shorter $((++i))

Also you can use for loop then your code becomes much cleaner:

for (( i=0; i < 5; i++ ))
do
  awk -v k=$i 'int($2)==k && $1=="r"  && $4==0 {pkt += $6} END {print k":"pkt}'  out.tr 
done