why variable increment in Shell does not work?

[flashcoder]

Hi,
I am abit puzzled with something that appears to be simplest thing to do - increment counter as it goes through "while" cycle. Here is a piece of code fragment, all I wan to do is to increment variable "num" and then log the result. But the counter num always shows 0 and I cant understand where is my problem. You might say that the condition if [[ "$filename" == *.xml ]] never happens but it does - the files get moved but the counter does not increase.

    num=0
    ls -1 ./$timestamp/$stendname > ./$timestamp/$stendname.lst
    cat ./$timestamp/$stendname.lst |
    while read filename
    do
      if [[ "$filename" == *.xml ]]
      then
        mv "./$timestamp/$stendname/$filename" "./in/$id-$filename"
        num=$((num+1))
      fi
    done
    echo -ne "number of retrieved files: $num ;"
    [ `ls -1 ./$timestamp/$stendname | wc -l` == 0 ] && rmdir ./$timestamp/$stendname || echo -ne "not deleting $stendname directory, some files left! "
    echo "done."

Strange is that when I do that straight in command line then it works, but not inside this script. I've tried several other ways to increment a scalar variable but none worked, it always echo-ed that $num = 0:

      num=$[$num + 1]
      num=$((num +1))

did not work either..
I know that this must be something simple but I cant figure out anymore.
Ok the script has set -e at the beginning so I can use constructions like command || echo "error" but I dont think it has something to do with it.

Thanks.

[HROAdmin26]

Google => "bash scripting" => First Link

For any Bash scripting needs, bookmark this page.

[flashcoder]

Thanks for the link, I did bookmark it.
I did quick change to my script: (( num = 0 )) and then later in code (( num++ )) but unfortunatelly nothing changed, it still does not increment. I cant understand whats going on there..
In mean time will read thruogh appropriate sections in that LDP project..
I am not first time shell script writer but this one is somewhat special. There must be some very simple mistake, but where..

[HROAdmin26]

Bash Scripting - Loops

Example 10-14

#!/bin/bash

var0=0
LIMIT=10

while [ "$var0" -lt "$LIMIT" ]
#      ^                    ^
# Spaces, because these are "test-brackets" . . .
do
  echo -n "$var0 "        # -n suppresses newline.
  #             ^           Space, to separate printed out numbers.

  var0=`expr $var0 + 1`   # var0=$(($var0+1))  also works.
                          # var0=$((var0 + 1)) also works.
                          # let "var0 += 1"    also works.
done                      # Various other methods also work.

echo

exit 0