echo command color not working

Question

I have a code like this:

#!/bin/bash

COLOR_REST='\e[0m'
COLOR_GREEN='\e[0;32m'
echo -e "${COLOR_GREEN}OK${COLOR_REST}"

When I copy and paste the code into my iTerm, it displays OK in the color of green.

However, when I store the code in a file named testColor.sh, and execute ./testColor.sh. It displays \e[0;32mOK\e[0m on my screen.

Why doesn't it display OK with green?

I've also tried bash testColor.sh, and sh testColor.sh. Both fail to display the text in green.

Another thing I feel strange is that I don't see the -e option in the BSD General Commands Manual in man echo.

I'm using macOS High Sierra as my operating system.

Answer 1

Use

#!/bin/bash

COLOR_REST="$(tput sgr0)"
COLOR_GREEN="$(tput setaf 2)"
printf '%s%s%s\n' $COLOR_GREEN 'OK' $COLOR_REST

which uses printf to avoid echo options and tput to be portable across different terminals.

Answer 2

Using printf instead of echo should work in any POSIX compliant shell. I tried this in High Sierra with the default terminal and it didn't work (there weren't any extended options, just -n).

As for an explanation, I haven't used iTerm so I'm not completely sure, but could be a different echo implementation by iTerm, which would cause the flag to work only when using iTerm itself, not /bin/bash. Notice that in the man page for echo, it says

NOTE: your shell may have its own version of echo, which usually supersedes the version described here. Please refer to your shell's documentation for details about the options it supports.