Reading file line by line (with space) in Unix Shell scripting - Issue

Question

I want to read a file line by line in Unix shell scripting. Line can contain leading and trailing spaces and i want to read those spaces also in the line. I tried with "while read line" but read command is removing space characters from line :( Example if line in file are:-

abcd efghijk
 abcdefg hijk

line should be read as:- 1) "abcd efghijk" 2) " abcdefg hijk"

What I tried is this (which not worked):-

while read line
do
   echo $line
done < file.txt

I want line including space and tab characters in it. Please suggest a way.

Answer 1

Try this,

IFS=''
while read line
do
    echo $line
done < file.txt

EDIT:

From man bash

IFS - The Internal Field Separator that is used for word
splitting after expansion and to split lines into words
with  the  read  builtin  command. The default value is
``<space><tab><newline>''

Answer 2

You want to read raw lines to avoid problems with backslashes in the input (use -r):

while read -r line; do
   printf "<%s>\n" "$line"
done < file.txt

This will keep whitespace within the line, but removes leading and trailing whitespace. To keep those as well, set the IFS empty, as in

while IFS= read -r line; do
   printf "%s\n" "$line"
done < file.txt

This now is an equivalent of cat < file.txt as long as file.txt ends with a newline.

Note that you must double quote "$line" in order to keep word splitting from splitting the line into separate words--thus losing multiple whitespace sequences.