How do I determine if a terminal is color-capable?

Question

I would like to change a program to automatically detect whether a terminal is color-capable or not, so when I run said program from within a non-color capable terminal (say M-x shell in (X)Emacs), color is automatically turned off.

I don't want to hardcode the program to detect TERM={emacs,dumb}.

I am thinking that termcap/terminfo should be able to help with this, but so far I've only managed to cobble together this (n)curses-using snippet of code, which fails badly when it can't find the terminal:

#include <stdlib.h> #include <curses.h>  int main(void) {  int colors=0;   initscr();  start_color();  colors=has_colors() ? 1 : 0;  endwin();   printf(colors ? "YES\n" : "NO\n");   exit(0); } 

I.e. I get this:

$ gcc -Wall -lncurses -o hep hep.c $ echo $TERM xterm $ ./hep YES $ export TERM=dumb $ ./hep            NO $ export TERM=emacs $ ./hep             Error opening terminal: emacs. $  

which is... suboptimal.

Answer 1

A friend pointed me towards tput(1), and I cooked up this solution:

#!/bin/sh  # ack-wrapper - use tput to try and detect whether the terminal is #               color-capable, and call ack-grep accordingly.  OPTION='--nocolor'  COLORS=$(tput colors 2> /dev/null) if [ $? = 0 ] && [ $COLORS -gt 2 ]; then     OPTION='' fi  exec ack-grep $OPTION "$@" 

which works for me. It would be great if I had a way to integrate it into ack, though.