Download latest version of stack and create arch linux package

update_stack.sh

#!/bin/bash

installDir=/usr/bin
srcDir=src
pkgDir=pkg

function prepareEnv {
    mkdir -p "$srcDir"
}

function cleanEnv {
    rm -rf "$srcDir"
    rm -rf "$pkgDir"
    rm "PKGBUILD"
}

function getUrl {
    local findHeader="location: "
    local returl=https://get.haskellstack.org/stable/linux-x86_64.tar.gz
    local realurl="$(curl -I ${returl} 2>/dev/null | grep --color=never ${findHeader})"
    local realurl="${realurl:${#findHeader}}"
    echo -n "$realurl"
}

function getVersion {
    local url="$1"
    local verre="\/download\/v([0-9.]*)\/"
    [[ $url =~ $verre ]]
    local version="${BASH_REMATCH[1]}"
    echo -n "$version"
}

function checkVersion {
    local newVer="$1"
    local curVer="$(stack --version)"
    local verre="Version ([0-9.]*)"
    [[ $curVer =~ $verre ]]
    curVer="${BASH_REMATCH[1]}"

    local newToks=(${newVer//./ })
    local curToks=(${curVer//./ })

    if [[ "${#newToks[@]}" -le "${#curToks[@]}" ]]; then
        local numToks="${#newToks[@]}"
    else
        local numToks="${#curToks[@]}"
    fi

    for ((i=0; i < "$numToks"; i++)); do
        if [[ "${newToks[$i]}" -gt "${curToks[$i]}" ]]; then
            local retval=1
            break
        elif [[ "${newToks[$i]}" -lt "${curToks[$i]}" ]]; then
            local retval=0
            break
        fi
    done

    return $retval
}

function generatePkgBuild {
    local ver="$1"
    pkgbuild="pkgname=stack\npkgver=${ver}\npkgrel=1\npkgdesc=\"haskell tool stack\"\narch=('x86_64')\nlicense=('GPL')\ndepends=('pacman>=5.1')\n\npackage() {\n    cd \"\$srcdir\"\n    mkdir -p \"\$pkgdir/${installDir}\"\n    cp stack \"\$pkgdir/${installDir}\"\n}\n"
    echo -ne "$pkgbuild" > PKGBUILD
}

function createPackage {
    makepkg
}

function updateStack {
    local url="$1"
    local ver="$2"
    local urlToks=(${url//\// })
    local numToks="${#urlToks[@]}"
    local fname="${urlToks[$numToks-1]}"
    local dirname="${fname:0:-7}"

    curl -L "$url" > "$fname" 2>/dev/null
    tar -xzf "$fname"
    rm "$fname"
    mv "$dirname/stack" "$srcDir"
    rm -rf "$dirname"

    generatePkgBuild "$ver"
    createPackage
    cleanEnv
}

# Retrieve URL and Version
url="$(getUrl)"
ver="$(getVersion $url)"

# Delete line terminator
url="${url:0:-1}"

shouldUpdate=0
if [[ "$(command -v stack)" ]]; then
    checkVersion "$ver"
    shouldUpdate="$?"
else
    shouldUpdate=1
fi

if [[ "$shouldUpdate" -eq 1 ]]; then
    prepareEnv
    updateStack "$url" "$ver"
else
    echo "You have a current version of stack"
fi