console-text-color-themes.sh

#!/bin/bash
# @Function
# show all console text color themes.
#
# @online-doc https://github.com/oldratlee/useful-scripts/blob/dev-2.x/docs/shell.md#-console-text-color-themessh
# @author Jerry Lee (oldratlee at gmail dot com)
#
# NOTE about Bash Traps and Pitfalls:
#
# 1. DO NOT combine var declaration and assignment which value supplied by subshell!
#    for example: readonly var1=$(echo value1)
#                 local var1=$(echo value1)
#
#    declaration make exit code of assignment to be always 0,
#      aka. the exit code of command in subshell is discarded.
#      tested on bash 3.2.57/4.2.46

_ctct_READLINK_CMD=readlink
if command -v greadlink > /dev/null; then
    _ctct_READLINK_CMD=greadlink
fi

# NOTE: DO NOT declare var _ctct_PROG as readonly, because its value is supplied by subshell.
_ctct_PROG="$(basename "$($_ctct_READLINK_CMD -f "${BASH_SOURCE[0]}")")"
[ "$_ctct_PROG" == 'console-text-color-themes.sh' ] && readonly _ctct_is_direct_run=true

readonly _ctct_ec=$'\033'      # escape char
readonly _ctct_eend=$'\033[0m' # escape end

colorEcho() {
    local combination="$1"
    shift 1

    [ -t 1 ] && echo "${_ctct_ec}[${combination}m$*$_ctct_eend" || echo "$*"
}

colorEchoWithoutNewLine() {
    local combination="$1"
    shift 1

    [ -t 1 ] && echo -n "${_ctct_ec}[${combination}m$*$_ctct_eend" || echo -n "$*"
}

# if not directly run this script(use as lib), just export 2 helper functions,
# and do NOT print anything.
[ "$_ctct_is_direct_run" == "true" ] && {
    for style in 0 1 2 3 4 5 6 7; do
        for fg in 30 31 32 33 34 35 36 37; do
            for bg in 40 41 42 43 44 45 46 47; do
                combination="${style};${fg};${bg}"
                colorEchoWithoutNewLine "$combination" "$combination"
                echo -n " "
            done
            echo
        done
        echo
    done

    echo "Code sample to print color text:"

    echo -n '    echo -e "\033['
    colorEchoWithoutNewLine "3;35;40" "1;36;41"
    echo -n "m"
    colorEchoWithoutNewLine "0;32;40" "Sample Text"
    echo "\033[0m\""

    echo -n "    echo \$'\033["
    colorEchoWithoutNewLine "3;35;40" "1;36;41"
    echo -n "m'\""
    colorEchoWithoutNewLine "0;32;40" "Sample Text"
    echo "\"$'\033[0m'"
    echo "      # NOTE: $'foo' is the escape sequence syntax of bash, safer escape"

    echo "Output of above code:"
    echo "    ${_ctct_ec}[1;36;41mSample Text${_ctct_eend}"
    echo
    echo "If you are going crazy to write text in escapes string like me,"
    echo "you can use colorEcho and colorEchoWithoutNewLine function in this script."
    echo
    echo "Code sample to print color text:"
    echo '    colorEcho "1;36;41" "Sample Text"'
    echo "Output of above code:"
    echo -n "    "
    colorEcho "1;36;41" "Sample Text"
}