Docker args with whitespaces from variable. How to use it> - linux

Question

I have searched the answer at stackoverflow(and google too) for 3 hours and I didnt find correct solution.
In my CI a need to dynamicly add docker build arguments. And I need to use it from env variables.
I have a string with docker arg:
DOCKER_ARGS="CURL_ARGS='-k https://example.invalid/'|ARG2=As|ARG3=asdas"
In my *.sh I wrote some code:
DOCKER_ARGS="CURL_ARGS='-k https://example.invalid/'|ARG2=As|ARG3=asdas"
if [ ! -z "$DOCKER_ARGS" ]; then
ARG_LIST=()
while read -d"|" ARG || [[ -n "$ARG" ]];
do
ARG_LIST+=("--build-arg $ARG")
done <<<$DOCKER_ARGS
fi
docker build -t test . ${ARG_LIST[#]}
And when I use echo ${ARG_LIST[#]}, I receive correct result:
--build-arg CURL_ARGS='-k https://example.invalid/' --build-arg ARG2=As --build-arg ARG3=asdas
But when I use docker build -t test . ${ARG_LIST[#]} it gives me an error:
"docker build" requires exactly 1 argument.
And if I use echo for command:
echo "docker build -t test . ${ARG_LIST[#]}" - I had correct result
I expect that will works as:
docker build -t image:tag . --build-arg CURL_ARGS='-k https://example.invalid/' --build-arg ARG2=As --build-arg ARG3=asdas

Answer 1

There are some problems with your script.
DOCKER_ARGS="CURL_ARGS='-k https://example.invalid/'|ARG2=As|ARG3=asdas"
With current handling CURL_ARGS will be set to '-k https://example.invalid/' including the quotes. Either remove the quotes from the input, or write your own un-quoting removal routine.
read -d"|" ARG
Removes trailing and leading whitespaces from input because of IFS and interprets missing slash sequences because or missing -r.
ARG_LIST+=("--build-arg $ARG")
Assigns a single element with the value --build-arg $ARG to the array. You would have to split later on the space between build-arg and $ARG. Instead assign two elements - one for --build-arg and the other for $ARG.
A better script might look like the following:
docker_args="CURL_ARGS=-k https://example.invalid/|ARG2=As|ARG3=asdas"
arg_list=()
if [[ -n "$docker_args" ]]; then
# split input on `|`
# Potentially use readarray to handle newlines
IFS='|' read -r -a args <<<"$docker_args"
# Add --built-arg to arrays
for arg in "${args[#]}"; do
# Proper quoting
arg_list+=(--build-arg "$arg")
done
fi
# proper quoting
docker build -t test . "${arg_list[#]}"
Check your scripts with http://shellcheck.net . Re-research how quoting works in shell and to use bash arrays. Prefer to use lower case variable names.