When reading a line using While loop in bash, it's squezzing multiple space into one

Question

I am writing a shell Script to read the number of blank space into a file.

I am using following template to read line one by one

 while read l 
 do

 done <filename

but It's converting multiple spaces into one space while reading a line.

Answer 1

Akash, you are running into problems because you are failing to quote your variables which invites word-splitting of output from echo (and any of the other commands) giving the impression that whitespace was not preserved. To correct the problem, always Quote your variables, e.g.

#!/bin/bash

while IFS= read -r l 
do
    echo "$l"
    echo "$l" > tempf
    wc -L tempf | cat > length
    len=$(cut -d " " -f 1 length)
    echo "$len"
done < "$1"

Example Input File

$ cat fn
who -all
           system boot  2019-02-13 10:27
           run-level 5  2019-02-13 10:27
LOGIN      tty1         2019-02-13 10:27              1389 id=tty1
david    ? :0           2019-02-13 10:27   ?          3118
david    - console      2019-02-13 10:27  old         3118 (:0)

Example Use/Output

$ bash readwspaces.sh fn
who -all
8
           system boot  2019-02-13 10:27
40
           run-level 5  2019-02-13 10:27
40
LOGIN      tty1         2019-02-13 10:27              1389 id=tty1
66
david    ? :0           2019-02-13 10:27   ?          3118
58
david    - console      2019-02-13 10:27  old         3118 (:0)
63

Also, for what it is worth, you can shorten your script to:

#!/bin/bash

while IFS= read -r l 
do
    printf "%s\n%d\n" "$l" "${#l}"
done < "$1"