bash script function scope - linux

Question

function generateFileList {
for entry in "$ORIGINATION_PATH"/*
do
entry=${entry%.*} # retain the part before the dot
entry=${entry##*/} # retain the part after the last slash
if [ $(contains "${FILENAME[#]}" $entry) == "n" ]; then
FILENAME[$fn_counter]=$entry
fn_counter=(expr $fn_counter + 1)
echo $entry "added to filelist"
echo ${FILENAME[$fn_counter]}
fi
done
NUMBER_OF_FILES=$(expr ${#FILENAME[#]} + 1)}
I have this function .My $ORIGINATION_PATH has many files in it. However, when I call this function my $FILENAME array gets populated only with one entry.Why? Inside the function everything seems fine, and it seems that $FILENAME array gets all the values it needs to get, but when I check outside the function I only get one value in the $FILENAME aray

Answer 1

Problems with your code and suggestions for improvement:
You should initialize ${FILENAME[#]} to an empty array (either in the function itself if you always want the function to generate a new list of files from scratch, or before calling the function if you want to be able to build up a composite list of files by calling the function repeatedly on different base directories).
You should initialize $fn_counter to zero before starting the loop. Or, for the composite build-up idea, to the number of elements currently in ${FILENAME[#]}. Actually, another, perhaps preferable solution, would be to remove the $fn_counter variable entirely and replace it with ${#FILENAME[#]}, since it should always be equal to that value.
In the line fn_counter=(expr $fn_counter + 1), you're assigning $fn_counter to an array, rather than incrementing it. This is because you forgot the dollar before the open parenthesis. If you ran fn_counter=$(expr $fn_counter + 1) then it would work. But there's a better way to increment a numeric variable: let ++fn_counter.
You don't have to dollar-prefix variables in arithmetic expressions. So, for example, we can say ${FILENAME[fn_counter]} instead of ${FILENAME[$fn_counter]}.
You're trying to echo the element of ${FILENAME[#]} that was just added in the current iteration, but indexing it with $fn_counter after it was incremented, which is incorrect. You can solve this by subtracting 1 from it, i.e. echo "${FILENAME[fn_counter-1]}". Or, if removing $fn_counter, echo "${FILENAME[${#FILENAME[#]}-1]}".
When assigning $NUMBER_OF_FILES, I don't know why you're adding 1 to ${#FILENAME[#]}. The number of elements in the ${FILENAME[#]} array should be equal to the number of files, without requiring an increment, no? I recommend removing this variable entirely, since the value can be accessed directly as ${#FILENAME[#]}.
I recommend you pass inputs as arguments (e.g. pass $ORIGINATION_PATH as an argument) and use the local keyword to reduce the likelihood of variable clashes between functions. Globals are the default in bash, which creates dangerous possibilities for different functions to step on each others' toes. For example, imagine if the contains function (assuming it's a shell function) assigned a value to the global $entry variable.
I recommend always using the [[ command rather than [, as it's more powerful, and it's good to be consistent.
As written, your script won't work correctly on an empty directory. You could test in advance if the directory is empty (e.g. [[ -n "$(find "$ORIGINATION_PATH" -maxdepth 0 -empty)" ]]). Another solution is to set nullglob. Another solution is to skip glob words that don't actually exist (e.g. if [[ ! -e "$entry" ]]; then continue; fi;).
Always double-quote variable expansions to protect against word splitting, which takes place after variable expansion. For example, the contains call should be contains "${FILENAME[#]}" "$entry" (notice the double-quoting around $entry). The only exceptions are (1) when assigning a string variable to a string variable, i.e. new=$old, in which case you don't have to quote it, and (2) when expanding a numeric variable, which is guaranteed not to be corrupted by word splitting.
Here's a working solution, filling in the missing pieces:
function contains {
local target="${#:$#:1}";
local -a array=("${#:1:$#-1}");
local elem='';
for elem in "${array[#]}"; do
if [[ "$elem" == "$target" ]]; then
echo 'y';
return;
fi;
done;
echo 'n';
} ## end contains()
function generateFileList {
local path="$1";
local entry='';
for entry in "$path"/*; do
if [[ ! -e "$entry" ]]; then continue; fi;
entry=${entry%.*}; ## retain the part before the dot
entry=${entry##*/}; ## retain the part after the last slash
if [[ "$(contains "${FILENAME[#]}" "$entry")" == 'n' ]]; then
FILENAME[${#FILENAME[#]}]=$entry;
echo "$entry added to filelist";
echo "${FILENAME[${#FILENAME[#]}-1]}";
fi;
done;
} ## end generateFileList()
ORIGINATION_PATH='...';
FILENAME=(); ## build up result on global ${FILENAME[#]} var
generateFileList "$ORIGINATION_PATH";
echo "\${#FILENAME[#]} == ${#FILENAME[#]}";
echo "\${FILENAME[#]} == (${FILENAME[#]})";