place a multi-line output inside a variable

Question

I'm writing a script in bash and I want it to execute a command and to handle each line separately. for example:

LINES=$(df)
echo $LINES

it will return all the output converting new lines with spaces.

example:

if the output was supposed to be:

1
2
3

then I would get

1 2 3

how can I place the output of a command into a variable allowing new lines to still be new lines so when I print the variable i will get proper output?

Upholsterer

Answer 1

Generally in bash $v is asking for trouble in most cases. Almost always what you really mean is "$v" in double quotes:

LINES="$(df)"
echo "$LINES"

Alegre

Actually neither assignment to variable needs quotes, because result of expansion is not word-split when assigning to variable. But they don't hurt anything and it's easier to train your muscle-memory to just type double quotes around all expansions. – Nancee

Answer 2

No, it will not. The $(something) only strips trailing newlines.

The expansion in argument to echo splits on whitespace and than echo concatenates separate arguments with space. To preserve the whitespace, you need to quote again:

echo "$LINES"

Note, that the assignment does not need to be quoted; result of expansion is not word-split in assignment to variable and in argument to case. But it can be quoted and it's easier to just learn to just always put the quotes in.

Nancee

Are you sure? I got the expected results just with LINES=$(df); echo "${LINES}", perhaps IFS is different in our environment. Still +1 as $(df) is better than single backtick quotes in @kubanczyk's answer – Carpous

@nhed: Right... assignment to variable never splits. I got confused by error message that turned out to be coming from something else when I tested it here. – Nancee

@nhed: $() is preferred over ``, because it's easier to see and because it is easier to nest. – Nancee

@Alegre back-ticks is old school, first it is not easy on the eyes (back-ticks within double quotes), second it limits what you can do. Embedding 2 commands, For example: echo $$ > /tmp/mypid; LINES=$(ps $(cat /tmp/mypid)); echo "${LINES}" works ... the same with backticks won't – Carpous