Capturing multiple line output into a Bash variable


Question

I've got a script 'myscript' that outputs the following:

abc
def
ghi

in another script, I call:

declare RESULT=$(./myscript)

and $RESULT gets the value

abc def ghi

Is there a way to store the result either with the newlines, or with '\n' character so I can output it with 'echo -e'?

1
524
2/18/2017 5:18:36 AM

Accepted Answer

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).

986
8/4/2014 8:33:02 PM

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).


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