Array variable shows wrong command result length when no results

Question

I want to execute a command, store the result in an array, and know its size. The problem is that when I assign the command result to an array, it will show size 1 even if the command returned no results.

DEVICES=$(some|command)
echo "${#DEVICES[*]}" # Prints 1

However, if I do it manually, it works fine:

a=0
for i in $(some|command);
do
    a=$((a + 1))
done
echo "$a" # Prints 0

How can I assign the result to a variable and have the correct length?

Songy deleted answer below was correct, it was my mistake, copied his solution wrong... DEVICES=( $(some|command) ) works just fine. — m0skit0
– m0skit0, Commented Jul 21, 2015 at 13:24
I'll undelete it then ;P Didn't want people doing the wrong thing :P — Songy
– Songy, Commented Jul 21, 2015 at 13:25
@m0skit0 No problem :P Was furiously typing into a terminal to figure out what it could be :P — Songy
– Songy, Commented Jul 21, 2015 at 13:27
@EtanReisner It doesn't matter, when you declare a variable then it automatically has an "array length" of 1. Try var="";echo "${#var[*]}" — 123
– 123, Commented Jul 21, 2015 at 13:28

Songy · Accepted Answer · 2015-07-21 13:18:02Z

3

You need to make DEVICES an array.

Change DEVICES=$(some|command) to DEVICES=( $(some|command) )

At the moment it is just a single string

answered Jul 21, 2015 at 13:18

Songy

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1 Comment

Etan Reisner Over a year ago

Note that this both word-splits and expands globs/etc. So this isn't a generally safe pattern to use.

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