[SOLVED] Help in using 'awk' programming........

apanimesh061 · 11-20-2010, 07:03 AM

I have a text file with 4 columns and 18 rows. All are integers.
I wish to find the average of first 12 numbers in the third column using 'awk'.

Please help !!!!
ASAP
Thanks......

grail · 11-20-2010, 07:38 AM

Sure. Where are you getting stuck? It appears a fairly trivial problem that would easily be solved with some searching.

H_TeXMeX_H · 11-20-2010, 09:14 AM

Yup, it has been asked before. ASAP = homework due tomorrow ?

Here's an awk reference:
http://www.grymoire.com/Unix/Awk.html

apanimesh061 · 11-21-2010, 06:23 AM

@ H TEXMEX H.....
I checked out the link.......I was good.....helped me a lot......
Running awk commands in the terminal was easy to some extent. The main problem arising is in Shell code.

Code:

#!/bin/awk -f
BEGIN 
{

    total=0;
}

{
   total+=$3;
}
END 
{

    print lines " lines read";
    print "total is ", total;
    if (lines > 0 ) {
	print "average is ", total/NR;
    } else {
	print "average is 0";
    }
}

This shell is correct...but at the terminal how will I execute it ?????
I also wanted to know the use of '#! /bin/awk -f'
Please help...!!!!!

H_TeXMeX_H · 11-21-2010, 06:34 AM

Well, here's something that might work:

Code:

awk '{lines++; if (lines <= 12) {sum+=$3}; if (lines == 12) print sum/12}' test.txt

Note that variables are always initialized in awk, so you don't actually have to.

grail · 11-21-2010, 07:30 AM

Or as you are already using NR just use it from the start:

Code:

 awk 'NR<=12{total+=$3}NR==12{print total/NR}' file

MTK358 · 11-21-2010, 07:45 AM

Quote:

Originally Posted by apanimesh061

I also wanted to know the use of '#! /bin/awk -f'
Please help...!!!!!

http://en.wikipedia.org/wiki/Shebang_line

H_TeXMeX_H · 11-21-2010, 07:57 AM

Quote:

Originally Posted by grail

Or as you are already using NR just use it from the start:

Code:

 awk 'NR<=12{total+=$3}NR==12{print total/NR}' file

You're right, this is better. However, I still like if statements to make it more readable.

crts · 11-21-2010, 09:06 AM

I do recall that there was a similiar problem a couple of days ago. Using NR is problematic if the file contains blank lines. So to deal with blank lines:

Code:

awk '($3~/[0-9]+/ && c<3){t+=$3;c++}END{print t/c}' file

As for your Shebang issue:
On my system awk is located in /usr/bin/. So you might also have to change your Shebang to '#!/usr/bin/awk -f'.
However, I see a windows logo in your posts. Are you running awk from windows? I am not sure if windows handles something like Shebangs. I *think* it doesn't.

In any case here is some more info on Shebangs:
http://en.wikipedia.org/wiki/Shebang_%28Unix%29
http://wiki.linuxquestions.org/wiki/Shebang
http://tldp.org/LDP/abs/html/sha-bang.html