grep using array values and make it faster

Question

array[1] is a string pulled from a 30k lines CSV: example:

samsung black 2014

I need match those lines with one of the values contained within an array (arrayItems).

arrayItems contains 221 values like:

apple
sony
samsung

The actual script:

while IFS=$';' read -r -a array
do
    mapfile -t arrayItems < $itemsFile
    ## now loop through the above array
    for itemToFind in "${arrayItems[@]}"
    do
       itemFound=""
       itemFound="$(echo ${array[1]} | grep -o '^$itemToFind')"
       if [ -n "$itemFound" ] 
       then 
          echo $itemFound 
          # so end to search in case the item is found
          break
       fi
    done
   # here I do something with ${array[2]}, ${array[4]} line by line and so on, 
   # so I can't match the whole file $file_in at once but online line by line.
done < $file_in

The problem is that grep don't match.

but works If I try to hardcode $itemToFind like this:

itemFound="$(echo ${array[1]} | grep -o '^samsung')"

Another thing is... how to do it faster as $file_in is a 30k lines CSV?

Answer 1

You can use grep with file pattern option (-f)

Example:

$ echo -e "apple\nsony\nsamsung" > file_pattern
$ grep -f file_pattern your.csv

EDIT: In response of your new contraints:

sed 's/^/\^/g' $itemsFile > /tmp/pattern_file
while IFS=$';' read -r -a array
do
    echo ${array[1]} | grep -q -f /tmp/pattern_file.txt
    if [ $? -eq 0 ]; then 
        # here I do something with ${array[2]}, ${array[4]} line by line and so on, 
        # so I can't match the whole file $file_in at once but online line by line.
    fi
done < $file_in

Answer 2

There are two errors in your script:

• grep tries to match the string $itemToFind because you put it between single quote '. Use double-quote instead.

• you are using an array from index 1 while help read tells it is starting at zero.

This should give this:

while IFS=$';' read -r -a array
do
    mapfile -t arrayItems < $itemsFile
    ## now loop through the above array
    for itemToFind in "${arrayItems[@]}"
    do
       itemFound=""
       itemFound=$(echo ${array[0]} | grep -o "$itemToFind")
       if [ -n "$itemFound" ] 
       then 
          echo $itemFound 
          # so end to search in case the item is found
          break
       fi
    done
done < $file_in

EDIT:

If you want to make it faster, you can use extended regular expressions :

grep -E 'apple|sony|samsung' $file_in

And if you want to display only brands:

grep -E 'apple|sony|samsung' $file_in | awk '{print $1}'