How can I test if the output of my program contains color (codes)?

Question

The program I'm working on has an option to enable/disable the color codes in it's output.

I want to test if this feature works as expected. This is what I tried:

$ myprogram | grep -q '\e[32m' # testing for green color
$ myprogram | grep -q '\e'
$ myprogram | grep -q '\033'

I also tried the same commands with double backslashes and without quotes.

But none of this works.

How can test if my program output contains any color codes?

Answer 1

The grep command, with both its BRE and ERE variants, does not recognise a sequence representing ESC. You need either to use the perl extension (GNU grep -P) or match on a fixed shell string.

# string with shell formatting, grep uses fixed string match
( tput setaf 2; echo Green text; tput op ) | grep -Fq $'\033[32' && echo found green
found green

# grep uses Perl's PCRE match to match any colour (change "\d+" to "32" for just green)
( tput setaf 2; echo Green text; tput op ) | grep -Pq '\033\[\d+[;m]' && echo found a colour
found a colour

If your shell supports $'...string here...' formatting of strings, and you only need to match for a specific colour, I'd recommend you take that option.

Answer 2

Another thing you can do is use 'tr' to turn the escape character into something else, especially if there is a character like ^ or % or even ^A (control-A), which grep does seem to be happy with:

boldfoo=$(printf "not bold \033[1mfoo\033[m not bold")

echo $boldfoo
echo $boldfoo | tr '\033' '\001' | grep ^V^A  # Type <Ctrl-V><Ctrl-A>
# Use the return value from this to see whether there are escape characters in $boldfoo.

I have used this trick to use sed/grep to find multiline patterns -- turn into ^A, and then match on a pattern with ^A, etc. Takes some finagling as the entire input is now a single line, but it works with some effort.