Bash unbound variable array (script: s3-bash) - bash

Question

I am working with: s3-bash, when I run it in my local environment (OS X 10.10.1) I don't have any problems, when I try to run it on a ubuntu server 14.04.1 I get the following error:
./s3-common-functions: line 66: temporaryFiles: unbound variable
./s3-common-functions: line 85: temporaryFiles: unbound variable
I've looked at the s3-common-functions script and the variable looks to be initialized properly (as an array):
# Globals
declare -a temporaryFiles
But there is a note in the comment, and I'm sure if it's related:
# Do not use this from directly. Due to a bug in bash, array assignments do not work when the function is used with command substitution
function createTemporaryFile
{
local temporaryFile="$(mktemp "$temporaryDirectory/$$.$1.XXXXXXXX")" || printErrorHelpAndExit "Environment Error: Could not create a temporary file. Please check you /tmp folder permissions allow files and folders to be created and disc space." $invalidEnvironmentExitCode
local length="${#temporaryFiles[#]}"
temporaryFiles[$length]="$temporaryFile"
}

Answer 1

There appears to be a bash behaviour change at play here.
Found by kojiro: CHANGES
hhhh. Fixed a bug that caused `declare' and `test' to find variables that
had been given attributes but not assigned values. Such variables are
not set.
$ bash --version
GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.
$ set -u
$ declare -a tF
$ echo "${#tF[#]}"
0
vs.
$ bash --version
GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ set -u
$ declare -a tF
$ echo "${#tF[#]}"
0
vs.
$ bash --version
GNU bash, version 4.3.30(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ set -u
$ declare -a tF
$ echo "${#tF[#]}"
-bash: tF: unbound variable
You can use declare -a tF=() on the newer bash versions to work around this.
$ declare -a tF=()
$ echo "${#tF[#]}"
0

Answer 2

Bash can substitute an empty value into unset variables using a dash.
set -u
my_array=()
printf "${my_array[#]-}\n"
This specific example will print nothing, but it will not give you an unbound variable error either.
Stolen from Bash: Error `Unbound variable' when appending to empty array1.
However, when used for a loop, you get one iteration (not zero) then:
for i in "${my_array[#]-}"
do
echo $i
done
Expectation might be to get zero iterations.
It could be fixed this way then:
[ ${#my_array[#]} -gt 0 ] &&
for i in "${my_array[#]}"
do
echo $i
done

Answer 3

Changed declaration of array for temporaryfiles
declare -a temporaryFiles
to:
temporaryFiles=()
Why this is different / non-function in ubuntu 14.04.1 Linux 3.13.0-32-generic x86_64 versus OS X I am not sure ?

Answer 4

find $fullfolder -type f |
while read fullfile
do
filename=$(basename "$fullfile")
ext=$([[ $filename = *.* ]] && printf %s ${filename##*.} || printf 'NONE')
arr+=($ext)
echo ${#arr[#]}
done
echo ${#arr[#]}
Why does the ${#arr[#]} inside the for loop produce the correct result but the one outside gives 0?