bash tee remove color

Question

I'm currently using the following to capture everything that goes to the terminal and throw it into a log file

exec 4<&1 5<&2 1>&2>&>(tee -a $LOG_FILE)

however, I don't want color escape codes/clutter going into the log file. so i have something like this that sorta works

exec 4<&1 5<&2 1>&2>&>(
    while read -u 0; do
        #to terminal
        echo "$REPLY"
        #to log file (color removed)
        echo "$REPLY" | sed -r 's/\x1B\[([0-9]{1,2}(;[0-9]{1,2})?)?[m|K]//g' >> $LOG_FILE
    done
    unset REPLY #tidy
)

except read waits for carriage return which isn't ideal for some portions of the script (e.g. echo -n "..." or printf without \n).

---

Follow-up to Jonathan Leffler's answer:

Given the example script test.sh:

#!/bin/bash

LOG_FILE="./test.log"
echo -n >$LOG_FILE

exec 4<&1 5<&2 1>&2>&>(tee -a >(sed -r 's/\x1B\[([0-9]{1,2}(;[0-9]{1,2})?)?[m|K]//g' > $LOG_FILE))


##### ##### #####
# Main

echo "starting execution"
printf "\n\n"

echo "color test:"
echo -e "\033[0;31mhello \033[0;32mworld\033[0m!"
printf "\n\n"

echo -e "\033[0;36mEnvironment:\033[0m\n  foo: cat\n  bar: dog\n  your wife: hot\n  fix: A/C"
echo -n "Before we get started. Is the above information correct?  "
read YES
echo -e "\n[READ] $YES" >> $LOG_FILE
YES=$(echo "$YES" | sed 's/^\s*//;s/\s*$//')
test ! "$(echo "$YES" | grep -iE '^y(es)?$')" && echo -e "\nExiting... :(" && exit
printf "\n\n"

#...some hundreds of lines of code later...

echo "Done!"


##### ##### #####
# End

exec 1<&4 4>&- 2<&5 5>&-

echo "Log File: $LOG_FILE"

1. The output to the terminal is as expected and there is no color escape codes/clutter in the log file as desired. However upon examining test.log, I do not see the [READ] ... (see line 21 of test.sh).

2. The log file [of my actual bash script] contains the line Log File: ... at the end of it even after closing the 4 and 5 fds. I was able to resolve the issue by putting a sleep 1 before the second exec - I assume there's a race condition or fd shenanigans to blame for it. Unfortunately for you guys, I am not able to reproduce this issue with test.sh but I'd be interested in any speculation anyone may have.

Answer 1

Consider using the pee program discussed in Is it possible to distribute stdin over parallel processes. It would allow you to send the log data through your sed script, while continuing to send the colours to the actual output.

One major advantage of this is that it would remove the 'execute sed once per line of log output'; that is really diabolical for performance (in terms of number of processes executed, if nothing else).