Python downloader/installer

install-python.sh

#!/bin/bash

#
# Summary: Installs/upgrades python installations on your machine.
#
# Prerequisites:
#  - jq and curl to be installed and in a folder on the PATH environment variable
#  - PLATFORM and STORAGE_FOLDER variables below to be set correctly (did not take time to automatically pick)
#

usage() {
  echo "Usage: $0 [-v | --version <version prefix>] [-a | --additional-version] [-h | --help]" >&2;
  echo " -v <version> -- What version to install (e.g., '3', '3.10', '3.10.0') - latest with prefix is installed" >&2;
  echo " -a           -- Don't replace current version - install additional" >&2;
  echo " -u           -- Upgrade if available -- or do nothing if already installed" >&2;
  echo " -h           -- Show this help and exit" >&2;
}
die() {
  echo $* >&2;
  exit 1;
}

# Substring to match in the download filename for this platform -- see download link values on the website to pick one
PLATFORM='embed-amd64';
# Where you want the distributions to be stored
STORAGE_FOLDER='/c/repos/app';

# www.python.org api documentation (more or less): https://github.com/python/pythondotorg/blob/main/downloads/api.py
RELEASE_INFO_URL="https://www.python.org/api/v2/downloads/release/";
FILE_INFO_URL_BASE="https://www.python.org/api/v2/downloads/release_file/";
DOWNLOAD_FOLDER="$STORAGE_FOLDER/python-current";

# Defaults
VERSION_PREFIX=3;
ADDITIONAL=no;
UPGRADE=no;

while [ $# -gt 0 ]; do
  case $1 in
    -v | --version)
      shift;
      VERSION_PREFIX="$1";
      ;;
    -a | --additional-version)
      ADDITIONAL=yes;
      ;;
    -u | --upgrade)
      UPGRADE=yes;
      ;;
    -h | --help)
      usage;
      exit;
      ;;
    *)
      usage;
      die "unrecognized option $1";
      ;;
  esac;
  shift;
done;

if ! which jq >/dev/null 2>&1; then
  echo "You must have jq installed and in a path in the PATH environment variable for this to work.";
fi;

echo -e "\nDetermining version information";
VERSION_PREFIX_PATTERN="$(echo "$VERSION_PREFIX" | sed -e 's/[^.0-9]//g; s/\./\\\\./g')";

# Sort by version (descending) then take the first (latest) one
JQ_PATTERN='def lpad(n):
  tostring |
  if n > length then
    ((n-length)*"0") + .
  else
    .
  end;

[
  .[]
  | select(.name | match(" '$VERSION_PREFIX_PATTERN'\\.\\d$"))]
  | sort_by(
    .name
    | split(" ")
    | .[1]
    | split(".")
    | map(select(test("\\d")))
    | map(tonumber | lpad(3))
    | join("."))
  | reverse
  | .[0]';

RELEASE_INFO_JSON="$(curl "$RELEASE_INFO_URL" | jq "$JQ_PATTERN" -r)";
VERSION="$(echo "$RELEASE_INFO_JSON" | jq '.name | split(" ") | .[1]' -r)"
RELEASE_RESOURCE_URI="$(echo "$RELEASE_INFO_JSON" | jq '.resource_uri' -r)";
RELEASE_NUMBER="$(basename "$RELEASE_RESOURCE_URI")";
FILE_INFO_URL="${FILE_INFO_URL_BASE}?release=${RELEASE_NUMBER}";

DOWNLOAD_URL=$(curl "$FILE_INFO_URL" | jq '.[].url | select(contains("'$PLATFORM'"))' -r);
if [ $ADDITIONAL = "yes" ]; then
  DOWNLOAD_FOLDER="$STORAGE_FOLDER/python-$VERSION";
  if [ -e "$DOWNLOAD_FOLDER" ] && [ $UPGRADE != "yes" ]; then
    die "Can't download additional version because folder already exists.  Delete and run again: $DOWNLOAD_FOLDER";
  fi;
fi;

if [ $(echo "$DOWNLOAD_FOLDER" | tr '/' ' ' | wc -w) -lt 2 ]; then
  die "Refusing to write to $DOWNLOAD_FOLDER because it has less than 2 slashes -- don't want to risk breaking root folder";
fi;

if [ -e "$DOWNLOAD_FOLDER" ]; then
  if [ -e "$DOWNLOAD_FOLDER/python" ] && [ "$("$DOWNLOAD_FOLDER/python" --version)" = "Python $VERSION" ]; then
    echo "Version $VERSION already appears to be installed at $DOWNLOAD_FOLDER - doing nothing.";
    exit;
  fi;
  rm -rf "$DOWNLOAD_FOLDER";
fi;

echo -e "\nActually performing download/install of the software from $DOWNLOAD_URL";
mkdir -p "$DOWNLOAD_FOLDER";
cd "$DOWNLOAD_FOLDER";
case "$DOWNLOAD_URL" in
  *.zip)
    curl "$DOWNLOAD_URL" -o "_archive.zip";
    unzip "_archive.zip";
    ;;
  *.tar.gz)
    curl "$DOWNLOAD_URL" | tar -xzv;
    ;;
  *)
    die "Don't know how to handle file extension of download url: $DOWNLOAD_URL";
    ;;
esac;

if echo "$DOWNLOAD_URL" | grep "embed" >/dev/null; then
  echo -e "\nInstalling pip";
  PTH_FILE=
  sed -i 's/^#//' "$DOWNLOAD_FOLDER/"python*._pth;
  curl "https://bootstrap.pypa.io/get-pip.py" | "$DOWNLOAD_FOLDER/python" || die "Unable to install pip.  See error for details.";
fi;

echo -e "\nVerifying installation";
if [ "$("$DOWNLOAD_FOLDER/python" --version)" != "Python $VERSION" ]; then
  die "Something seems to be wrong with the installation -- maybe wrong architecture?  Check the platform parameter variable in the script and see any error output directly above this message to troubleshoot.";
fi;

echo -e "\nInstalled to $DOWNLOAD_FOLDER successfully!  You can ues it from there explicitly or add it to your PATH environment variable to use.";