bash, for loop, and arithmetic

rmount · 05-22-2007, 03:39 PM

Hello all, i've been scratching my head on this one. I'm not sure what i've done wrong.

I've got a bunch of subdirectories, each with a log file in them. I'm grepping the files for an error count, then totaling the number. Here's the script i'm using:

Code:

#!/bin/bash
#
# Error counter
# ---------------------

file="error.log"
number=0
total=0

for dir in /var/log/mht*
do
    number=`grep -i ^errorcount $dir/$file | awk -F'=' '{ print $2 }'`
    number=$(( $number + $total ))
done

echo "Total error count = $total"

exit

My total is always 0. Can anyone see what i'm doing wrong, or give me another way to skin the cat?

Thanks!

macemoneta · 05-22-2007, 03:43 PM

You're not setting total to anything other than zero in the initialization. You probably want that second assignment in the loop to be "total="...

Matir · 05-22-2007, 03:44 PM

Nothing ever gets added to total.

Perhaps where you said number=$(( $number + $total )) you meant total=...?

rmount · 05-22-2007, 03:59 PM

Quote:

Originally Posted by Matir

Nothing ever gets added to total.

Perhaps where you said number=$(( $number + $total )) you meant total=...?

Duh... Been playing around with it so much. I corrected that. Also had to re-order it to this:

Code:

total=$(( $total + $number ))

If i use "total=$(( $number + $total ))" the script hangs.

So with the corrected script, i now get this:

Code:

 : syntax error: operand expected (error token is " ")

makyo · 05-22-2007, 05:05 PM

Hi.

Probably a variable that is not initialized.

Old school: echo the variables before the assignment.

Newer school: run the script with "-vx":

Code:

sh -vx file-in-which-script-resides

Best wishes ... cheers, makyo

rmount · 05-22-2007, 08:51 PM

Quote:

Originally Posted by makyo

Newer school: run the script with "-vx":

Here's the output:

Code:

#!/bin/bash
#
# Error counter
# ---------------------

file="error.log" 
+ file=error.log
number=0
+ number=0
total=
+ total=

for dir in /var/log/mht*
do 
    number=`grep -i ^errorcount $dir/$file | awk -F'=' '{ print $2 }'`
    total=$(( $total + $number )) 
    echo $total
done 
grep -i ^errorcount $dir/$file | awk -F'=' '{ print $2 }'
++ grep -i '^errorcount' /var/log/mht-001/error.log
++ awk -F= '{ print $2 }'
+ number=10
+ total=10
+ echo 10
10
grep -i ^errorcount $dir/$file | awk -F'=' '{ print $2 }'
++ grep -i '^errorcount' /var/log/mht-002/error.log
++ awk -F= '{ print $2 }'
+ number=10
 : syntax error: operand expected (error token is " ")

So it runs the first pass just fine, then bails on the total of the second file.

I tried echoing before assignment and get the same error

Matir · 05-22-2007, 09:11 PM

I'm wondering if it might be a whitespace issue in $number. Try something (silly as it seems) like "number=`echo $number`".

rmount · 05-22-2007, 09:27 PM

Quote:

Originally Posted by Matir

I'm wondering if it might be a whitespace issue in $number. Try something (silly as it seems) like "number=`echo $number`".

Good thought. I added that in before the "total=$(($total+$number))" and it still gives the same error

ghostdog74 · 05-22-2007, 09:43 PM

Code:

awk 'BEGIN{FS="="}/^errorcount/{ count+=$2}END{print "total: "count}' /var/log/mht*/error.log

rmount · 05-22-2007, 09:55 PM

Quote:

Originally Posted by ghostdog74

Code:

awk 'BEGIN{FS="="}/^errorcount/{ count+=$2}END{print "total: "count}' /var/log/mht*/error.log

Simple, yet genius. Thanks Ghostdog74, that did the trick and replaces almost all of the script

Matir · 05-22-2007, 10:46 PM

Man, I need to learn awk.

rmount · 05-22-2007, 10:54 PM

Quote:

Originally Posted by Matir

Man, I need to learn awk.

I agree, that and sed. I've only ever used either in a very basic way.

sidney.harrell · 05-22-2007, 11:09 PM

For some light reading...
http://www.gnu.org/software/gawk/manual/gawk.html
Great, just what I needed, another complete language to learn. There are not enough hours in the day.

Quote:

On one of many trips to the library or bookstore in search of books on Unix, I found the gray AWK book, a.k.a. Aho, Kernighan and Weinberger, The AWK Programming Language, Addison-Wesley, 1988. AWK's simple programming paradigm—find a pattern in the input and then perform an action—often reduced complex or tedious data manipulations to few lines of code. I was excited to try my hand at programming in AWK.

Is that the same Kernighan from the C language fame?

AnanthaP · 05-23-2007, 01:27 AM

total = `expr $total + $number`

End