Splitting by newlines

Question

Have been using different bash function implementations that is able to process separate lines in arguments.

var1="
First Argument
A new line"
var2="
Second Argument
A new line"

Calling the function as

theone $var

to disallow word splitting.

But then inside the function, I still have to to quote $@.

theone ()
 {
  for vl in "$@"; do
    printf '%s\n' "$vl"
  done
 }

What I want is to split by newline.

Answer 1

Calling theone $var splits on every word in $var: the first argument is First, the second is Argument, the third is A, and so on. You will lose your embedded newlines with this approach, and as with any unquoted variable any word in the string that contains a shell wildcard (*, [, ], ?) will be subject to globbing and matched against names in the current directory. A string such as "Are you sure??" could be expanded to "Are you surety" if you had a file called surety in the current directory. Generally, not a good idea.

Based on your previous question I would suggest that's supposed to be written theone "$var", where word splitting does not take place and you have a single multi-line argument to theone.

If you want to process each line of $var separately I can suggest a number of different constructs. In each, the printf line is written to show clearly what is being processed in the inner loop. Call each as theone "$var":

1. POSIX

   theone()
   {
       printf '%s\n' "$@" |
           while IFS= read -r vl
           do
               printf '## vl: %s ##\n' "$vl"
           done
   }
   

2. Shells such as bash

   theone()
   (
       for arg in "$@"
       do
           while IFS= read -r vl
           do
               printf '## vl: %s ##\n' "$vl"
           done <<< "$arg"
       done
   )
   

3. Also shells such as bash

   theone()
   (
       for arg in "$@"
       do
           readarray -t vls <<<"$arg"
       for vl in &quot;${vls[@]}&quot;
       do
           printf '## vl: %s ##\n' &quot;$vl&quot;
       done
   done
   
   )
   

All of these can be simplified by removing the outermost loop if you really only want to pass a single (multi-line) argument. For example, the last one could be written like this:

4. Shells such as bash

   theone()
   {
       local vls vl
   readarray -t vls <<<"$1"
   
   for vl in "${vls[@]}"
   do
       printf '## vl: %s ##\n' "$vl"
   done
   
   }