I am having trouble removing new lines from text in a shell script (using sed and grep) - shell

Question

I am using zsh on macOS
I have a shell script that produces a text file with speedtest results in the following layout:
Download: 63.57 Mbps (data used: 69.3 MB)
Upload: 16.11 Mbps (data used: 23.0 MB)
I can manipulate the layout and produce this:
↓ 63.57 Mbps |
↑ 16.11 Mbps
Note the line break before the first line of text and the one after the pipe. In the Terminal only the final line is printed out: ↑ 16.11 Mbps
The script to transform the input is this:
DOWNLOAD=$(cat ~/Terminal_Projects/temp_speedtest_result.txt | grep Download | sed 's/ Download: /↓ /g' | sed 's/ (data used: //g' | sed -E 's/[0-9]{1,4}\.[0-9] MB)//g' | sed 's/\n\r\t//')
UPLOAD=$(cat ~/Terminal_Projects/temp_speedtest_result.txt | grep Upload | sed 's/ Upload: /↑ /g' | sed 's/ (data used: //g' | sed -E 's/[0-9]{1,4}\.[0-9] MB)//g' | tr '\n' ' ')
RESULT=$DOWNLOAD" | "$UPLOAD
echo $RESULT
I used multiple instances of sed because I couldn't get it to work in just one instance. You may know how to get it to work.
What I want to do is output the DOWNLOAD and UPLOAD variables on a single line. I have another very similar script that achieves that with exactly the same manipulation of variables.
What I have tried:
Using RESULT="$DOWNLOAD | $UPLOAD"
Using RESULT="${DOWNLOAD} | ${UPLOAD}"
Using tr '\n' ' ' instead of the sed command to remove \n
I tried removing the up and down arrows in case those symbols aren't supported - same behaviour.
I have tried using sed on the RESULT variable to try removing new lines. I also tried writing the contents of the RESULT variable to a new temp txt file and then retrieving the contents of the file and using grep to extract the results one by one in the hope the new lines would not be copied. Didn't work for me.
It looks like there are line breaks that I have been unable to remove but I could be wrong.
I am new to command line and shell scripts. Trying to apply my very limited knowledge to a new scenario. Any help would be appreciated.

Answer 1

tr seems to do the job and echo -n "$UPLOAD" shows on a single line, so I think you're on the right track and only need to fix the DOWNLOAD part.
I suggest you simplify the script a bit using something along these lines:
INPUT_FILE="~/Terminal_Projects/temp_speedtest_result.txt"
DOWNLOAD="$(grep Download $INPUT_FILE | awk '{print "↓" $2 " " $3}' | tr '\n' ' ')"
UPLOAD="$(grep Upload $INPUT_FILE | awk '{print "↓" $2 " " $3}' | tr '\n' ' ')"
echo "$DOWNLOAD | $UPLOAD"

Answer 2

How about
RESULT="$(grep -Ew '(Down|Up)load' <~/Terminal_Projects/temp_speedtest_result.txt | tr '\n' ' ')"
? This is more efficient (only one grep and tr process needed) and also fixes the bug you have in your solution by your use of a pipe in RESULT=$DOWNLOAD" | "$UPLOAD (which should have brought up an error message).