String concatenation in Bash script

Question

I am writing this Bash script:

count=0   
result

for d in `ls -1 $IMAGE_DIR | egrep \"jpg$\"`
do

    if (( (count % 4) == 0 )); then
                result=\"a         


        

Answer 1

The = operator must always be written without spaces around it:

result="$result $d"

(Pretty much the most important difference in shell programming to normal programming is that whitespace matters in places where you wouldn't expect it. This is one of them.)

Answer 2

Something like this?

count=0   

find $IMAGE_DIR -name "*.jpg" |
while read f; do
        if (( (count % 4) == 0 )); then
                result="abc $f"

                if (( count > 0 )); then
                        echo $result
                fi

        else
                result="$result $d"
        fi

        (( count++ ))
done

Answer 3

Something like this (untested, of course):

count=0 result=

for d in "$IMAGE_DIR"/*jpg; do
   (( ++count % 4 == 0 )) &&
     result="abc $d"
   (( count > 0 )) &&
     printf '%s\n' "$result" ||
      result+=$d
done