Bash get last line from a variable

Question

If I have a variable with multiple lines (text) in it, how can I get the last line out of it?

I already figured out how to get the first line:

STRING="This is a
multiple line
variable test"
FIRST_LINE=(${STRING[@]})
echo "$FIRST_LINE"

# output:
"This is a"

Probably there should be an operator for the last line. Or at least I assume that because with @ the first line comes out.

Your script output is only first word of variable (This), not all line. — Mustafa DOGRU, Sep 21 '16 at 11:27
Oh, didn't get that. Maybe because in my use case the first line is only a single word. *phew* — Matt Backslash, Sep 21 '16 at 11:29
If you need to do such manipulations, don't store the lines in a string but in an array! — gniourf_gniourf, Sep 21 '16 at 11:34
`STRING` is not an array, so `${STRING[@]}` isn't really any different from `$STRING`. — chepner, Sep 21 '16 at 11:34

score 79 · Answer 1 · answered Sep 21 '16 at 11:23

79

An easy way to do this is to use tail:

echo "$STRING" | tail -n1

answered Sep 21 '16 at 11:23

redneb

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anubhava · Accepted Answer · 2016-09-21T11:27:43.700

35

Using bash string manipulations:

$> str="This is a
multiple line
variable test"

$> echo "${str##*$'\n'}"
variable test

${str##*$'\n'} will remove the longest match till \n from start of the string thus leaving only the last line in input.

edited Sep 21 '16 at 11:27

answered Sep 21 '16 at 11:26

anubhava

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chepner · Answer 3 · 2016-09-21T11:36:30.357

2

If you want an array with one element per line from STRING, use

readarray -t lines <<< "$STRING"

Then, the first line would be ${lines[0]}, and the last line would be ${lines[-1]}. In older versions of bash, negative indices aren't allowed and you'll have to compute the last index manually: ${lines[${#lines[@]}-1]}.

edited Sep 21 '16 at 11:36

answered Sep 21 '16 at 11:31

chepner

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A small note may be stating need `bash 4.x`? – Inian Sep 21 '16 at 11:44
IMO, 3.x should just be treated as a POSIX-compatible shell on par with `dash`, but with better features for interactive use. I consider the nearly 6-year-old `bash` 4.2 release a reasonable baseline assumption now. – chepner Sep 21 '16 at 11:54
Still using `GNU bash, version 4.1.2` btw :), in which it is not supported. :( Thought would be good point to add for a proper reference. – Inian Sep 21 '16 at 11:57
I also consider knowing what version of `bash` you are using to be part of your due diligence in asking a question. I am no longer presenting a laundry list of options to cater to 3 or more different versions of `bash` in every answer. I'm taking Python as my model, where the assumption is that you are using Python 3.3+ unless otherwise stated, and Python 2 pretty much means Python 2.7. – chepner Sep 21 '16 at 12:06
Cheers! no disrespect meant! – Inian Sep 21 '16 at 12:07
1

None taken! This is a little rant that's been building in me for some time, and there's no good place for it :) I'd love to get some consensus and put a note in the `bash` tag info about what features we can reasonably assume, but no one asking questions reads that page anyway. – chepner Sep 21 '16 at 12:22

Bash get last line from a variable

3 Answers3