UNIX for Dummies Questions & Answers

$ cat filename
#!/bin/bash
pw > script_output 2>err_log
## pw is the not working command to capture o/p in error logfile
## In place of pw, use your command to run
echo -e '\e[0;31m'; cat err_log ; echo -e '\e[0;00m'
$
$ bash filename
j: pw: command not found
$

#!/bin/sh

trap "rm -f fifo" EXIT

mkfifo fifo

exec 5>logfile

# Run a loop in the background that reads stderr data from fifo,
# prints to terminal and prints to logfile
( while read LINE
  do
        printf "\033[1;31m%s\033[0m\n" "$LINE" >&2
        echo "$LINE"
  done <fifo >&5 ) &

# The first () command is just a substitute for your command
# which prints to stderr and stdout.
# We redirect its stderr into the fifo, where the background
# loop will read it.
( echo asdf >&2 ; echo qwerty ) 2>fifo | while read LINE
do
        # Print to the logfile
        echo "$LINE" >&5
        # print to the screen
        echo "$LINE"
done
# close the logfile
exec 5>&-

rm -f fifo

# wait for the background loop to quit
wait