Common bash functions for creating install scripts

bash-install-util-functions.sh

#!/usr/bin/env bash

set -o nounset
set -o errtrace
set -o errexit
set -o pipefail

# Text color variables
declare -r txtund=$(tput sgr 0 1)          # Underline
declare -r txtbld=$(tput bold)             # Bold
declare -r failColor=${txtbld}$(tput setaf 1) #  red
declare -r warnColor=${txtbld}$(tput setaf 3) #  yellow
declare -r notice=${txtbld}$(tput setaf 4) #  blue
declare -r exampleColor=${txtbld}$(tput setaf 2) #  green
declare -r infoColor=${txtbld}$(tput setaf 7) #  white
declare -r txtrst=$(tput sgr0)             # Reset
declare -r isNumber='^[0-9]+$';

function prompt_yes_no () {
    local choice;
    builtin read -p "${notice}$1(y/n): ${txtrst}" -r choice;
    case $choice in
        y|Y) echo "yes";;
        n|N) echo "no";;
        *) echo "invalid";;
    esac
}


function say () {
    printf "${infoColor}%b${txtrst}\n" "$*";
}

function fail () {
    printf "${failColor}ERROR: %b${txtrst}\n" "$*";
    exit 1;
}
function warn () {
    printf "${warnColor}WARN: %b${txtrst}\n" "$*";
}
function example () {
    printf "${exampleColor}%b${txtrst}\n" "$*";
}

function prompt_string () {
    local answer;

    builtin read -p "${notice}$1: ${txtrst}" -r answer;
    if [ ! -z "$answer" ]; then
        echo $answer;
        return 0;
    else
        return 1;
    fi
}

function wait_for_keypress () {
    local answer;
    builtin read -n 1 -p "${notice}Press any key to continue${txtrst}" -r answer;
}


function open_url () {
    local -r url=$1;
    
    case "$(uname)" in
        Darwin)
            open $1;
            ;;
        Linux)
            BROWSER=${BROWSER:-};
            if [ ! -z "$BROWSER" ]; then
                $BROWSER "$url";
            elif which xdg-open > /dev/null; then
                xdg-open "$url";
            elif which gnome-open > /dev/null; then
                gnome-open "$url";
            else
                fail "Could not detect the web browser to use. Please visit $url manually.";
            fi
            ;;
        *)
            fail "Don't know how to open a browser on this platform. Please visit $url manually.";
            ;;
    esac
}

function abort_not_installed () {
    local -r progname=$1;
    local -r prog_url=$2;

    say "$progname doesn't seem to be installed!";
    local answer=$(prompt_yes_no \
        "Do you want to visit the $progname website to download and install it?");
    [[ $answer == "yes" ]] && open_url $prog_url;
    say "\nTry running this program again after you have installed $progname!";
    exit 2;
}

function abort_too_old () {
    local -r progname=$1;
    local -r prog_url=$2;
    local -r minver=$3;

    say "$progname is too old (need at least $minver)!";
    local answer=$(prompt_yes_no \
        "Do you want to visit the $progname website to upgrade it?");
    [[ $answer == "yes" ]] && open_url $prog_url;
    say "\nTry running this program again after you have upgraded $progname!";
    exit 2;
}


# http://stackoverflow.com/questions/4023830/bash-how-compare-two-strings-in-version-format
vercomp () {
    if [[ $1 == $2 ]]
    then
        return 0
    fi
    local IFS=.
    local i ver1=($1) ver2=($2)
    # fill empty fields in ver1 with zeros
    for ((i=${#ver1[@]}; i<${#ver2[@]}; i++))
    do
        ver1[i]=0
    done
    for ((i=0; i<${#ver1[@]}; i++))
    do
        if [[ -z ${ver2[i]} ]]
        then
            # fill empty fields in ver2 with zeros
            ver2[i]=0
        fi

        if ! [[ ${ver1[i]} =~ $isNumber ]] ; then
               return 3;
        fi

        if ((10#${ver1[i]} > 10#${ver2[i]}))
        then
            return 1
        fi
        if ((10#${ver1[i]} < 10#${ver2[i]}))
        then
            return 2
        fi
    done
    return 0
}

function found () {
    hash $1 2>&-;
}