How can I print text in various colors?

Do not hard-code ANSI color escape sequences in your program! The tput command lets you interact with the terminal database in a sane way: 

  # Bourne
  tput setaf 1; echo this is red
  tput setaf 2; echo this is green
  tput bold; echo "boldface (and still green)"
  tput sgr0; echo back to normal

Cygwin users: you need to install the ncurses package to get tput (see: Where did "tput" go in 1.7?)

tput reads the terminfo database which contains all the escape codes necessary for interacting with your terminal, as defined by the $TERM variable. For more details, see the terminfo(5) man page.

tput sgr0 resets the colors to their default settings. This also turns off boldface (tput bold), underline, etc.

If you want fancy colors in your prompt, consider using something manageable: 

  # Bash
  red=$(tput setaf 1)
  green=$(tput setaf 2)
  blue=$(tput setaf 4)
  reset=$(tput sgr0)
  PS1='\[$red\]\u\[$reset\]@\[$green\]\h\[$reset\]:\[$blue\]\w\[$reset\]\$ '

Note that we do not hard-code ANSI color escape sequences. Instead, we store the output of the tput command into variables, which are then used when $PS1 is expanded. Storing the values means we don't have to fork a tput process multiple times every time the prompt is displayed; tput is only invoked 4 times during shell startup. The \[ and \] symbols allow bash to understand which parts of the prompt cause no cursor movement; without them, lines will wrap incorrectly.

As an exception, if you are attempting to use tput with the PROMPT_COMMAND shell variable, remember, unlike most other variables, "the value of each set element [of the PROMPT_COMMAND array] is executed as a command prior to issuing each primary prompt," so the array value should be parsable as a command. 

pr_cmd_0='printf "%b" "${reset}"'
PROMPT_COMMAND=( [0]="${pr_cmd_0}" )

And here is a function to pick colors in a 256 color terminal 

# Bash
colors256() {
        local c i j

        printf "Colors 0 to 15 for the standard 16 colors\n"
        for ((c = 0; c < 16; c++)); do
                printf "|%s%3d%s" "$(tput setaf "$c")" "$c" "$(tput sgr0)"
        done
        printf "|\n\n"

        printf "Colors 16 to 231 for 256 colors\n"
        for ((i = j = 0; c < 232; c++, i++)); do
                printf "|"
                ((i > 5 && (i = 0, ++j))) && printf " |"
                ((j > 5 && (j = 0, 1)))   && printf "\b \n|"
                printf "%s%3d%s" "$(tput setaf "$c")" "$c" "$(tput sgr0)"
        done
        printf "|\n\n"

        printf "Greyscale 232 to 255 for 256 colors\n"
        for ((; c < 256; c++)); do
                printf "|%s%3d%s" "$(tput setaf "$c")" "$c" "$(tput sgr0)"
        done
        printf "|\n"
}

See also https://web.archive.org/web/20230405000510/https://wiki.bash-hackers.org/scripting/terminalcodes for an overview.

The following is a more extensive range of terminal sequence variables. Pick the ones you want: 

# Variables for terminal requests.
[[ -t 2 ]] && { 
    alt=$(      tput smcup  || tput ti      ) # Start alt display
    ealt=$(     tput rmcup  || tput te      ) # End   alt display
    hide=$(     tput civis  || tput vi      ) # Hide cursor
    show=$(     tput cnorm  || tput ve      ) # Show cursor
    save=$(     tput sc                     ) # Save cursor
    load=$(     tput rc                     ) # Load cursor
    bold=$(     tput bold   || tput md      ) # Start bold
    stout=$(    tput smso   || tput so      ) # Start stand-out
    estout=$(   tput rmso   || tput se      ) # End stand-out
    under=$(    tput smul   || tput us      ) # Start underline
    eunder=$(   tput rmul   || tput ue      ) # End   underline
    reset=$(    tput sgr0   || tput me      ) # Reset cursor
    blink=$(    tput blink  || tput mb      ) # Start blinking
    italic=$(   tput sitm   || tput ZH      ) # Start italic
    eitalic=$(  tput ritm   || tput ZR      ) # End   italic
[[ $TERM != *-m ]] && { 
    red=$(      tput setaf 1|| tput AF 1    )
    green=$(    tput setaf 2|| tput AF 2    )
    yellow=$(   tput setaf 3|| tput AF 3    )
    blue=$(     tput setaf 4|| tput AF 4    )
    magenta=$(  tput setaf 5|| tput AF 5    )
    cyan=$(     tput setaf 6|| tput AF 6    )
}
    white=$(    tput setaf 7|| tput AF 7    )
    default=$(  tput op                     )                                                                                                                                                                   
    eed=$(      tput ed     || tput cd      )   # Erase to end of display
    eel=$(      tput el     || tput ce      )   # Erase to end of line
    ebl=$(      tput el1    || tput cb      )   # Erase to beginning of line
    ewl=$eel$ebl                                # Erase whole line
    draw=$(     tput -S <<< '   enacs
                                smacs
                                acsc
                                rmacs' || { \
                tput eA; tput as;
                tput ac; tput ae;         } )   # Drawing characters
    back=$'\b'
} 2>/dev/null ||:

The above leaves the variables unset when stderr isn't connected to a terminal and leaves the color variables unset for monochrome terminals. The alternative tput executions allow the code to keep working on systems where tput takes old termcap names instead ANSI capnames. It also uses 2>/dev/null ||: to silence potential errors and avoid ERR script abortion. That allows this code to be used in a range of edge cases such as scripts that use set -e and terminals or OS's that don't support certain sequences (the code is borrowed from https://github.com/lhunath/scripts/blob/master/bashlib/bashlib ).

Discussion

This will be contentious, but I'm going to disagree and recommend you use hard-coded ANSI escape sequences because terminfo databases in the real world are too often broken.

tput setaf literally means "Set ANSI foreground" and shouldn't have any difference with a hard-coded ANSI escape sequence, except that it will actually work with broken terminfo databases so your colors will look correct in a VT with terminal type linux-16color or any terminal type so long as it really is a terminal capable of 16 ANSI colors.

So do consider setting those variables to hard-coded ANSI sequences such as: 

  # Bash
  white=$'\e[0;37m'

I'm also "old" and have worked with various terminals. I owned a WYSE 50 at one point. That was long ago; it's 2023 now. I'm against the recommendation to use tput. The tput command as such is described by POSIX, but not any specific actions that it performs. POSIX requires only the sub-commands clear, init and reset. Everything else is system-specific, nonstandard cruft. Meanwhile, ANSI/ECMA escape sequence are a standard which goes back to something like 1976. It's 2023 today; it's okay to specify that your script requires a terminal or terminal emulator that conforms to a standard we have had for at least fifty years. At least in production. If we are tinkering with old terminals for fun, that is a retrocomputing activity. There is nothing wrong with that, but FAQ answers should proably be be geared more toward production than tinkering around with old gear. -- KazKylheku

CategoryShell

BashFAQ/037 (last edited 2023-10-01 21:59:10 by larryv)