How can I preserve new lines coming from a command's output during variable assignment?

Question

Consider:

$ getfacl somefile.dat     # The output is formatted and contains several new lines..

# file: somefile.dat
# owner: user1
# group: group1
user::rw-
group::r--              #effective:r--
mask:r--
other:r--
$
$ ACL_PERMISSIONS=$(getfacl somefile.dat);
$ echo $ACL_PERMISSIONS;
# file: somefile.dat # owner: user1 # group: group1 user::rw- group::r-- #effective:r-- mask:r-- other:r--

So how do I preserve these new lines during variable assignment, so that when I echo $ACL_PERMISSIONS I get the same output as $ getfacl somefile.dat ..?

Solution

You need to quote your expansion, otherwise it will undergo word splitting, which is what you are experiencing.

acl=$(getfacl somefile.dat)
echo "$acl"

Bear in mind that $( strips trailing newlines anyway (it is considered a feature). If that is a problem for you, you need to do something like this to preserve them (in bash4+):

mapfile acl < <(getfacl somefile.dat)
printf %s "${acl[@]}"

Comments

[Kent Pawar]

Kindly explain the reason for the -1..?

[clerksx]

I'm not the downvoter, but my guess would be that it is because this is an issue merely involving missing quotes (which I don't think warrants a downvote, but I've seen it happen before on questions like this).

[Kent Pawar]

Hey @Chris, Thanks! I wasn't aware of 'word splitting' and using quotes around the variable does solve my problem.. Just curious, how can I preserve trailing newlines (not sure where such a thing might help) using ksh..?

[clerksx]

@KentPawar The first method should also work in ksh.

[clerksx]

@KentPawar From help mapfile: "[r]ead lines from the standard input into an indexed array variable". It essentially reads each line from the output of getfacl somefile.dat into an array called acl.

[suspectus]

$( strips newlines ? list=$(ls); echo $list; echo "$list" word splitting is demonstrated with echo $list, if newlines were stripped then I'd expect the same output with the 2nd echo.

[Kent Pawar]

@ChrisDown - thanks. But seems like mapfile does not come bundled with the Linux/Solaris boxes I am working on..

[suspectus]

@Kent - hmm strange, In ksh just tried the list=$(ls) etc (as above) and echo $list strips newlines, echo "$(list)" does not.

[suspectus]

@Kent - sorry for confusion. "strips newlines" is not a command it is just text. I think in your case you just need to enclose the variable in quotes as Chris suggested.

[clerksx]

@suspectus $( strips trailing newlines, not just any newlines.

[clerksx]

@KentPawar Just use the first example, in that case.