Shell that automatically trims spaces for no reason

December 5, 2022

Introduction

I was trying to do some instructions on a file line by line with:

while IFS= read -r line; do
    ...
done < file

When I noticed that there was a problem with trailing whitespaces (for example: " a " => "a") that were automatically deleted, which is a real problem for me.

I searched in the documentation and didn’t find any mention of that. And there is the same problem with printf.

Minimal example:

touch example # Create a file
echo "  exa    mple    " >> example # Add some text
cat example #    exa    mple    
echo $(cat example) # exa mple
rm example # Delete the file

In this example, I don’t understand why echo $(cat example) doesn’t have some trailing whitespaces.

And this "problem" is also here with:

while IFS= read -r line; do
    echo $line # exa mple
done < example

Version:

Tested with:

zsh v5.9
bash v5.2.2

>Solution :

IFS= read -r line < file is correctly reading unmodified lines with leading and trailing spaces. You can confirm this by printing the variable using declare -p line.

But after you read the lines correctly, you are mangling them during your print commands. Both echo $(cat example) and echo $line have unquoted expansions, which cause the shell to word-split your lines.

Quote them to resolve the problem: