while [ "$COUNTER" != "0" ]


it never reaches 0, so it has nothing left to do but a continuous loop of nothing, you need to break at somepoint

It should be in a for loop instead of while.

change

COUNTER=`ls -1 | wc -l`
while [ "$COUNTER" != "0" ]
to

COUNTER=`ls -1 | wc -l`
for (( $i=0; $i < "$COUNTER" ; i++ )); do

You're right, thanx.
However, this for loop is still missing the fact that variable COUNTER needs to decrease by 3 in every loop, or maybe add 3 to $i, What do you think?

for (( i=$COUNTER; $i > 0; )); do
echo $i
let i-=1
done

I hope this helps

I solved it!! Thanx for all sighK. This is the code for my script. It is used to move files (in my particular case were tiff images) from a folder to 3 different folders distributing the files among them. For example, if source folder has 100 files, the 3 target folders have to end up with 34, 33 and 33 files respectively. Hope this could be helpful to someone.

#!/bin/bash

COUNTER=`ls -1 *.TIF | wc -l`

while [ $COUNTER -gt 0 ]
do
        ARRAY=( $(ls *.TIF | head -n 3) )
        mv ${ARRAY[0]} folder1/
        mv ${ARRAY[1]} folder2/
        mv ${ARRAY[2]} folder3/
        COUNTER=`expr $COUNTER - 3`

done

The following is a bit shorter and allows an arbitrary number of folders

#!/bin/bash
i=1
for f in *.TIF; do
	mv "$f" "folder$i/"
	((i=i%3+1))
done