linux script example for loop

Example 1: loop bash

years=(2018 2019)
days=(74 274)

for year in "${years[@]}"; do
    for day in $(seq -w ${days[0]} ${days[1]}); do
               echo $year
               echo $day
    done
done

Example 2: loop bash

Use for in bash for iterating words in a string or values in an array as:
for value in {1, 2, 3}; do echo $value; done
for value in $(cat arguments_files.txt); do [some_command]; done
And use while for iterating lines from a pipe output as:
cat arguments_file.txt | while read line; do [some_command]; done