read -r var reads stdin into a variable

$ read -r greeting
   hello there!

(type here and press enter)

+ $ echo "$greeting"
hello there!

you can also read into multiple variables

$ read -r name1 name2 
ahmed fatima
$ echo "$name2" 
fatima

by default, read strips whitespace

" a b c " -> "a b c"

it uses the IFS (“Input Field Separator”) variable to decide what to strip

set IFS='' to avoid stripping whitespace empty string

$ IFS=''(empty string) read -r greeting

   hi there!
$ echo "$greeting"
   hi there!

the spaces are still there!

more IFS uses: loop over every line of a file

by default, for loops will loop over every word of a file (not every line). Set IFS='' to loop over every line instead!

(don’t forget to unset IFS when you’re done!)

IFS=''
for line in $(cat file.txt)
do
   echo $line
done