assign two bash arrays with a single command - arrays

Question

youtube-dl can take some time parsing remote sites when called multiple times.
EDIT0 : I want to fetch multiple properties (here fileNames and remoteFileSizes) output by youtube-dl without having to run it multiple times.
I use those 2 properties to compare the local file size and ${remoteFileSizes[$i]} to tell if the file is finished downloading.
$ youtube-dl --restrict-filenames -o "%(title)s__%(format_id)s__%(id)s.%(ext)s" -f m4a,18,webm,251 -s -j https://www.youtube.com/watch?v=UnZbjvyzteo 2>errors_youtube-dl.log | jq -r ._filename,.filesize | paste - - > input_data.txt
$ cat input_data.txt
Alan_Jackson_-_I_Want_To_Stroll_Over_Heaven_With_You_Live__18__UnZbjvyzteo__youtube_com.mp4 8419513
Alan_Jackson_-_I_Want_To_Stroll_Over_Heaven_With_You_Live__250__UnZbjvyzteo__youtube_com.webm 1528955
Alan_Jackson_-_I_Want_To_Stroll_Over_Heaven_With_You_Live__140__UnZbjvyzteo__youtube_com.m4a 2797366
Alan_Jackson_-_I_Want_To_Stroll_Over_Heaven_With_You_Live__244__UnZbjvyzteo__youtube_com.webm 8171725
I want the first column in the fileNames array and the second column in the remoteFileSizes.
For the time being, I use a while read loop, but when this loop is finished my two arrays are lost :
$ fileNames=()
$ remoteFileSizes=()
$ cat input_data.txt | while read fileName remoteFileSize; do \
fileNames+=($fileName); \
remoteFileSizes+=($remoteFileSize); \
done
$ for fileNames in "${fileNames[#]}"; do \
echo PROCESSING....; \
done
$ echo "=> fileNames[0] = ${fileNames[0]}"
=> fileNames[0] =
$ echo "=> remoteFileSizes[0] = ${remoteFileSizes[0]}"
=> remoteFileSizes[0] =
$
Is it possible to assign two bash arrays with a single command ?

Answer 1

You assign variables in a subshell, so they are not visible in the parent shell. Read https://mywiki.wooledge.org/BashFAQ/024 . Remove the cat and do a redirection to solve your problem.
while IFS=$'\t' read -r fileName remoteFileSize; do
fileNames+=("$fileName")
remoteFileSizes+=("$remoteFileSize")
done < input_data.txt
You might also interest yourself in https://mywiki.wooledge.org/BashFAQ/001.

Answer 2

For what it's worth, if you're looking for specific/bespoke functionality from youtube-dl, I recommend creating your own python scripts using the 'embedded' approach: https://github.com/ytdl-org/youtube-dl/blob/master/README.md#embedding-youtube-dl
You can set your own signal for when a download is finished (text/chime/mail/whatever) and track downloads without having to compare file sizes.