Bash wrapper to run a Python script using a virtual environment.

cron-safe-runner.bash

#!/usr/bin/env bash
# shellcheck shell=bash
# Bash wrapper to run Python scripts using a virtual environment.

set -Eeuo pipefail

# Constants
readonly HOME_DIR="${HOME}"
readonly VENV_DIR="${HOME_DIR}/path/to/venv"
readonly VENV_BIN="${VENV_DIR}/bin"
readonly ACTIVATE="${VENV_BIN}/activate"
readonly PYTHON_BIN="${VENV_BIN}/python3"

# Default scripts to run when no arguments are provided.
readonly -a SCRIPT_PATHS=(
  "${HOME_DIR}/path/to/repo/script_1.py"
  "${HOME_DIR}/path/to/repo/script_2.py"
  "${HOME_DIR}/path/to/repo/script_3.py"
)

# Google Cloud related: Explicitly export vars for crontab environment
export GOOGLE_CLOUD_PROJECT="<PROJECT_ID>"
export CREDENTIALS_FILE_PATH="${HOME_DIR}/path/to/<SERVICE_ACCOUNT_KEY>.json"
export GOOGLE_APPLICATION_CREDENTIALS="${HOME_DIR}/path/to/<ADC>.json"

log() {
  # Usage: log "message"
  printf '[%s] %s\n' "$(date '+%Y-%m-%d %H:%M:%S')" "$*" >&2
}

die() {
  # Usage: die "message"
  log "Error: $*"
  exit 1
}

validate_venv() {
  [[ -f "${ACTIVATE}" ]] || die "Virtual environment activate script not found at ${ACTIVATE}"
  [[ -x "${PYTHON_BIN}" ]] || die "Python interpreter not found/executable at ${PYTHON_BIN}"
}

resolve_scripts() {
  # If script paths were passed as arguments, use them; otherwise use defaults.
  # Prints resolved list (one per line) to stdout.
  if [[ "$#" -gt 0 ]]; then
    for s in "$@"; do
      printf '%s\n' "$s"
    done
  else
    for s in "${SCRIPT_PATHS[@]}"; do
      printf '%s\n' "$s"
    done
  fi
}

validate_scripts_exist() {
  # Usage: validate_scripts_exist <script1> <script2> ...
  for script in "$@"; do
    [[ -f "${script}" ]] || die "Python script not found at ${script}"
  done
}

run_scripts() {
  # Usage: run_scripts <script1> <script2> ...
  # Prefer executing via the venv's python directly (no need to source),
  # which avoids leaking environment changes to the caller.
  for script in "$@"; do
    log "Running: ${script}"
    "${PYTHON_BIN}" "${script}" || die "Failed to execute script ${script}"
  done
}

main() {
  validate_venv

  # Collect scripts from args or default list
  mapfile -t scripts < <(resolve_scripts "$@")
  validate_scripts_exist "${scripts[@]}"

  # Optionally activate if scripts rely on environment hooks; not required for running via PYTHON_BIN.
  # shellcheck disable=SC1090
  source "${ACTIVATE}" || die "Failed to activate virtual environment at ${VENV_DIR}"

  run_scripts "${scripts[@]}"
  log "All scripts completed successfully."
}

main "$@"