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Is there a reliable way to check how many colors my terminal emulator supports?

If echo $TERM prints xterm, does that unequivocally tell me how many colors my terminal emulator supports? How could I check this information reliably?

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The value of $TERM does not give much information about the number of supported colors. Many terminals advertise themselves as xterm, and might support any number of colors (2, 8, 16, 88 and 256 are common values).

You can query the value of each color with the OSC 4 ; c ; ? BEL control sequence. If the color number c is supported, and if the terminal understands this control sequence, the terminal will answer back with the value of the color. If the color number is not supported or if the terminal doesn't understand this control sequence, the terminal answers nothing. Here's a bash/zsh snippet to query whether color 42 is supported (redirect to/from the terminal if necessary):

printf '\e]4;%d;?\a' 42 if read -d $'\a' -s -t 1; then … # color 42 is supported

Among popular terminals, xterm and terminals based on the VTE library (Gnome-terminal, Terminator, Xfce4-terminal, …) support this control sequence; rxvt, konsole, screen and tmux don't.

I don't know of a more direct way.

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    Thanks @Gilles. This looks great. May I ask what read -d $'\a' -s -t 1 does? Commented Nov 1, 2011 at 22:50
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    @intrpc Read input until the first \a (bell character), without echoing input, with a timeout of 1 second. Commented Nov 1, 2011 at 22:55
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    @l0b0 tput colors queries the terminfo database. Chances are that you have TERM=xterm. Xterm can support at least 2, 8, 16, 88 or 256 colors depending on the version and on compile- and run-time options, but the terminfo database can only store one value. You can set e.g. TERM=xterm+256color, but then you'll be annoyed when you log in to a machine that doesn't have this entry in its termcap/terminfo database. Commented Nov 2, 2011 at 11:59
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    @l0b0 Your pipe obviously has nothing to do with the terminal. You need to print to the terminal (printf … >/dev/tty) and then read from the terminal (read … </dev/tty). Xterm responds to the OSC 4; …; ? BEL sequence by injecting keystrokes. Commented Feb 24, 2012 at 15:01
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    Awesome, thanks! Here's a script to determine how many colors your XTerm actually supports. Commented Feb 24, 2012 at 16:40
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You can use

$ tput colors

On my debian install tput is part of the ncurses-bin package which is installed by default.

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    That will only inform how many colors your terminal is reporting to the environment via TERM, not how many colors it can actually support given an appropriate TERM Commented Feb 3, 2015 at 23:31
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There is a perl script, 256colors2.pl, that will display all the colours on your terminal.

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