How to read commented line in a file and copy the same ..as it is to other file in shell script - shell

Question

I have file (Name test.func) with a comments as below
#--------------------
# DOG $ CAT NAMES
#--------------------
Brownie
Blacky
Vicky
Pammy
#--------------
# MOBILE & LAPTOP NAMES
#--------------
Lenovo
Oppo
Realme
The code i have written is as below
TestFile=$(cat /usr/test.func)
for line in $TestFile
echo "line is $line"
if [[ "$line" == *"#"* ]]; then
echo "$line is commented"
echo "$line" >>test_copy.func
echo " "
fi
if ...
#Some other logic here
fi
done
Output is giving as below (in test_copy.func)
line is #----------
#-------- is commented
line is #
# is commented
line is DOG
line is &
line is CAT
line is NAMES
*Some logic is performed*
line is #----------
#-------- is commented
line is #
# is commented
line is MOBILE
line is &
line is LAPTOP
line is NAMES
*Some logic is performed*
Expected output in test_copy.func should be as below
#--------------------
# DOG $ CAT NAMES
#--------------------
*Output as per the logic*
#--------------
# MOBILE & LAPTOP NAMES
#--------------
*Output as per the logic*
Commented lines are splited in the actual output.
But Expected result should be as in the source file
Can anyone help me to resolve this issue
code

Answer 1

The code:
TestFile=$(cat /usr/test.func)
for line in $TestFile
does not loop over the lines of the file, but over the "words" (contiguous strings of non-whitespace characters). The variable TestFile contains the contents of the file, but the for loop is subject to field splitting. In other words, if the file contains "foo bar baz", the loop is equivalent to for line in foo bar baz; do .... This is a very fragile construction, as it is also subject to glob expansion, etc. For example, if the file contains wildcards (eg foo * bar), those wildcards will be expanded (and foo * bar expands to a string that contains all the names in the current directory).
The standard way to iterate over the lines of a file is
while read line; do ... done < /usr/test.func
But this is terribly slow and should generally be avoided. Tools like sed and awk are far more appropriate. It's normally a bad idea to read through a file on multiple passes, but while read is so slow that you could read the file 50 times with other tools before you would likely begin to notice. You probably don't want to copy lines that merely contain a # (as the *"#"* expression will do, but only want to copy lines that begin with #, but that's a different question). I would recommend either:
sed -n -e '/^\s*#/p' /usr/test.func > test_copy.func
while read -r line; do some_other_logic "$line"; done < /usr/test.func
or:
awk '/^\s*#/{print > "test_copy.func"}
{ some other logic here }' /usr/test.func