How can I print text using any one of the 256 colors that the terminal allows?

Question

I would like to write a program that utilizes all 256 of the Linux terminal's text colors. To date, however, I have only found a handful of color codes, which are in the format "\033[1;NUMmNUM\033[1;m". However, these escape codes only allow for two or three dozen colors, not the 256 that the Linux terminal supposedly allows for. How can I display those other colors in my curses application?

Answer 1

You can have a look into TERM settings. It is possible it is set to lesser then capable string. To test colors you can run GNU's msgcat. Try e.g.:

echo $TERM
msgcat --color=test
TERM=xterm-256color
msgcat --color=test

Or use @Ignacio Vazquez-Abrams's loop instead of msgcat.

For more information on how and what to set have a look at e.g.:

• 256 colour terminals
• TERM strings
• TTY with 256 colors?
• … etc.

Answer 2

Stop using escape codes and use the setaf terminfo capability instead.

$ for i in $(seq 0 $(tput colors) ) ; do tput setaf $i ; echo -n "█" ; done ; tput setaf 15 ; echo

Answer 3

TERM tells tput (and other applications that use the terminal database) how many colors your terminal (supposedly) supports and how to set the foreground (setaf) and background (setab) for that.

The example script is close, but doesn't reset properly:

for i in $(seq 0 $(tput colors) ) ; do tput setaf $i ; echo -n "█" ; done ; echo ; tput op

Here is a screenshot from xterm to illustrate:

For what it's worth, msgcat uses the terminal database, but then follows up with some hardcoded assumptions about the terminal's color capability. Some of that needs rethinking, e.g., noticing a coding error for instance in this line:

               (strlen (term) >= 4 && memcmp (term, "rxvt", 7) == 0)