Why echo is printing string variables before additional text that have been merged with it?

Question

I have code in bash for making latex file and in this fragment I want to make a table in a loop:

  while IFS= read -r line; do
    if [[ "$line" == *"comment"* ]]; then
  echo "${line#*comment: }" >> tif_list.txt

  IN="${line#*comment: }"

  data="$(echo $IN | tr "," "\n")"

  echo "       ${data[0]}" >> table.tex #name
  echo "     & ${data[2]}" >> table.tex #longitude
  echo "     & ${data[3]}" >> table.tex #latitude
  echo "     & ${data[4]}, ${data[5]}, ${data[6]}, ${data[7]}, ${data[8]}, ${data[9]}, " >> table.tex #dimensions
  echo "     & ${data[10]}" >> table.tex #time
  echo "     & ${data[1]}" >> table.tex #comments
  echo "     & \includegraphics[width=3.5cm]{${tif%.*}.png}\\" >> table.tex #adress
  echo "    \hline" >> table.tex
  echo "" >> table.tex

fi    

done < tif_info.txt
done

but echo first prints variables, and then my additional text:

     \hline
       Target0001
The operator places target notes here. Multiple lines OK.
55:51.6217 N
020:34.4421 E
C1
L3.0
W0.8
H1-1.0
H2-1.0
D16.8
2021:11:13 08:29:02.37
     & 
     & 
     & , , , , , , 
     & 
     & 
     & \includegraphics[width=3.5cm]{Target0001.png}\
    \hline

I want:

     \hline
     Target0001
     & The operator places target notes here. Multiple lines OK.
     & 55:51.6217 N
     & 020:34.4421 E
     & C1, L3.0, W0.8, H1-1.0, H2-1.0, D16.8 
     & 2021:11:13 08:29:02.37
     & \includegraphics[width=3.5cm]{Target0001.png}\
    \hline

I was trying to add /& or merge text by += but it doesn't change anything. I just need to make it work so I could have table with pictures and metadata from my tiff pictures.

My whole code:

#!/bin/bash
#program pobiera metadane tiff i zestawia w tabeli
echo "Starting..."
echo "\documentclass{article}" > table.tex
echo "\usepackage{graphicx, tabularx}" >> table.tex
echo "\usepackage[margin=0.5in]{geometry}" >> table.tex
echo "\graphicspath{ {./images/} }" >> table.tex
echo "" >> table.tex
echo "\renewcommand\tabularxcolumn[1]{m{#1}}" >> table.tex
echo "\newcolumntype{b}{X}" >> table.tex
echo "\newcolumntype{s}{>{\hsize=.5\hsize}X}" >> table.tex
echo "" >> table.tex
echo "\begin{document}" >> table.tex
echo "" >> table.tex
echo "\begin{table}[htbp]" >> table.tex
echo "    \centering" >> table.tex
echo "    \begin{tabularx}{\textwidth} { " >> table.tex
echo "      | >{\centering\arraybackslash}s " >> table.tex
echo "      | >{\centering\arraybackslash}s " >> table.tex
echo "      | >{\centering\arraybackslash}s " >> table.tex
echo "      | >{\centering\arraybackslash}s " >> table.tex
echo "      | >{\centering\arraybackslash}s " >> table.tex
echo "      | >{\centering\arraybackslash}b " >> table.tex
echo "      | >{\centering\arraybackslash}b | }" >> table.tex
echo "     \hline" >> table.tex
echo "     name & longitude & latitude & dimensions & time & comments & picture \" >> table.tex
echo "     \hline" >> table.tex
echo "Serching comment..."
for tif in *.tif; do
  [ -f "$tif" ] || break
  identify -verbose "$tif" > tif_info.txt 2>&1
#convert "$tif" "${tif%.*}.png" 2>&1
while IFS= read -r line; do
    if [[ "$line" == "comment" ]]; then
  echo "${line#*comment: }" >> tif_list.txt

  IN="${line#*comment: }"

  data="$(echo $IN | tr "," "\n")"

  echo "       ${data[0]}" >> table.tex #name
  echo "     & ${data[2]}" >> table.tex #longitude
  echo "     & ${data[3]}" >> table.tex #latitude
  echo "     & ${data[4]}, ${data[5]}, ${data[6]}, ${data[7]}, ${data[8]}, ${data[9]}, " >> table.tex #dimensions
  echo "     & ${data[10]}" >> table.tex #time
  echo "     & ${data[1]}" >> table.tex #comments
  echo "     & \includegraphics[width=3.5cm]{${tif%.*}.png}\\" >> table.tex #adress
  echo "    \hline" >> table.tex
  echo "" >> table.tex

fi    

done < tif_info.txt
done
echo "    \hline" >> table.tex
echo "    \end{tabularx}" >> table.tex
echo "\end{table}" >> table.tex
echo "" >> table.tex
echo "\end{document}" >> table.tex
echo "" >> table.tex
echo "Process completed."

Answer 1

data="$(echo $IN | tr "," "\n")"

This is a scalar assignment, so you get a scalar variable. It'll contain a single multi-line string. (You could check with declare -p data.) In Bash,$var and ${var[0]} access the same element, regardless of the type of the variable. Either the one at index 0 if it's an array, or the lone value if it's a scalar.

You probably want to use read -a instead, e.g.

IN=foo,bar,doo
IFS=, read -r -a data  <<< "$IN"
echo "${#data[@]}" "${data[1]}"   # prints '3 bar'

---

In the stackexchange question you linked to, there's this:

mails=$(echo $IN | tr ";" "\n")
for addr in $mails
do ...

There, it's the unquoted expansion of $mails in the for loop that splits the contents on whitespace (or rather, whatever IFS contains, but by default it's whitespace). Now, that works, and you could similarly assign the result to an array with arr=($mails), but it'll split on any whitespace, and it'll process filename patterns, so values like foo bar and * will be trouble. See e.g http://mywiki.wooledge.org/WordSplitting and When is double-quoting necessary?

The top answer there has the same read -a that I wrote above. You want the -r too, to prevent it from messing up backslashes.