Input from file

Sometimes we want to use a file instead. In the example below we have a file with a lot of car brands, listed one per line. You can find the file in examplefolder.

filename="cars.txt"
re="^[C-E].*$"
IFS=$'\n'

for car in $(< "$filename"); do
    [[ $car =~ $re ]] && echo "$car"
done

Above we match the cars that start with C, D or E. Since the cars can have names separated by space, we set IFS to newline.

To avoid changing IFS in the entire environment, we can restructure the code so that we only change IFS for the read command:

filename="cars.txt"
re="^[C-E].*$"

while IFS=$'\n' read -r car; do
    [[ $car =~ $re ]] && echo "$car"
done < $filename

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