Capturing multiple line output into a Bash variable

Actually, RESULT contains what you want — to demonstrate:

echo "$RESULT"

What you show is what you get from:

echo $RESULT

As noted in the comments, the difference is that (1) the double-quoted version of the variable (echo "$RESULT") preserves internal spacing of the value exactly as it is represented in the variable — newlines, tabs, multiple blanks and all — whereas (2) the unquoted version (echo $RESULT) replaces each sequence of one or more blanks, tabs and newlines with a single space. Thus (1) preserves the shape of the input variable, whereas (2) creates a potentially very long single line of output with 'words' separated by single spaces (where a 'word' is a sequence of non-whitespace characters; there needn't be any alphanumerics in any of the words).

Another pitfall with this is that command substitution — $() — strips trailing newlines. Probably not always important, but if you really want to preserve exactly what was output, you'll have to use another line and some quoting:

RESULTX="$(./myscript; echo x)"RESULT="${RESULTX%x}"

This is especially important if you want to handle all possible filenames (to avoid undefined behavior like operating on the wrong file).

In case that you're interested in specific lines, use a result-array:

declare RESULT=($(./myscript))  # (..) = arrayecho "First line: ${RESULT[0]}"echo "Second line: ${RESULT[1]}"echo "N-th line: ${RESULT[N]}"