Looping over files to find a particular line in those files

search.sh

#! /bin/bash
# @description outputs lines and the files they came from to an arbitrary file
# @argument input {String} - regex looking for files in local directory
# @argument output {Filename} - where to echo found lines to
# @argument searchstring {String} - what to match for
# @example - ./search.sh '*.csv' outputfile.csv portuguese
echo $1
for file in $1; do
  echo "Examining $file"

  cat $file | while read line; do

    if [[ $line == *"$3"* ]]; then
      echo $file >> $2
      echo $line >> $2
    fi

  done

done