Multi-line string with extra space (preserved indentation)

Question

I want to write some pre-defined texts to a file with the following:

text="this is line one\n this is line two\n this is line three"  echo -e $text > filename 

I'm expecting something like this:

this is line one this is line two this is line three 

But got this:

this is line one  this is line two  this is line three 

I'm positive that there is no space after each \n, but how does the extra space come out?

Answer 1

Heredoc sounds more convenient for this purpose. It is used to send multiple commands to a command interpreter program like ex or cat

cat << EndOfMessage This is line 1. This is line 2. Line 3. EndOfMessage 

The string after << indicates where to stop.

To send these lines to a file, use:

cat > $FILE <<- EOM Line 1. Line 2. EOM 

You could also store these lines to a variable:

read -r -d '' VAR << EOM This is line 1. This is line 2. Line 3. EOM 

This stores the lines to the variable named VAR.

When printing, remember the quotes around the variable otherwise you won't see the newline characters.

echo "$VAR" 

Even better, you can use indentation to make it stand out more in your code. This time just add a - after << to stop the tabs from appearing.

read -r -d '' VAR <<- EOM     This is line 1.     This is line 2.     Line 3. EOM 

But then you must use tabs, not spaces, for indentation in your code.

Answer 2

If you're trying to get the string into a variable, another easy way is something like this:

USAGE=$(cat <<-END     This is line one.     This is line two.     This is line three. END ) 

If you indent your string with tabs (i.e., '\t'), the indentation will be stripped out. If you indent with spaces, the indentation will be left in.

NOTE: It is significant that the last closing parenthesis is on another line. The END text must appear on a line by itself.