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boilerplate.md

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I'm Australian

User

give me some bash boilerplate that:

• checks bashes version and refuses to run if its older than current
• sets up all safe and desirable shopts: globbing and lastpipe, not nullglob or whatever
• Sets up boot, machine, and invocation id from systemd's id stuff
• sets up variables for all the XDG dirs
• sets up an array called "TRAP_EXIT" that will run on the exit trap

ChatGPT

Here’s a Bash script boilerplate that:

• Verifies that the Bash version is at least a specific minimum version.
• Enables strict/safe shell options (e.g., set -euo pipefail and useful shopt flags).
• Pulls boot, machine, and invocation IDs from systemd.
• Sets up XDG directory variables with sensible fallbacks.
• Defines a TRAP_EXIT array to register exit trap commands cleanly.

#!/usr/bin/env bash

# === Minimum Bash Version Check ===
REQUIRED_BASH_MAJOR=5
REQUIRED_BASH_MINOR=0

if ((BASH_VERSINFO[0] < REQUIRED_BASH_MAJOR)) || 
   ((BASH_VERSINFO[0] == REQUIRED_BASH_MAJOR && BASH_VERSINFO[1] < REQUIRED_BASH_MINOR)); then
    echo "Error: Bash $REQUIRED_BASH_MAJOR.$REQUIRED_BASH_MINOR or newer is required." >&2
    exit 1
fi

# === Safe Shell Options ===
set -euo pipefail
IFS=$'\n\t'

# Recommended shell options
shopt -s globstar      # Allow ** to match nested directories
shopt -s extglob       # Enable extended globbing
shopt -s lastpipe      # Allow lastpipe to work in non-interactive shells
shopt -u nullglob      # Don't expand globs to null string if nothing matches
shopt -u failglob      # Don't fail if globs don't match

# === Systemd IDs ===
BOOT_ID=$(cat /proc/sys/kernel/random/boot_id 2>/dev/null || echo "")
MACHINE_ID=$(cat /etc/machine-id 2>/dev/null || echo "")
INVOCATION_ID=$(journalctl --flush && grep -F 'invocation_id=' /proc/self/environ | tr '\0' '\n' | cut -d= -f2 || echo "")

# === XDG Directory Setup ===
XDG_CACHE_HOME="${XDG_CACHE_HOME:-$HOME/.cache}"
XDG_CONFIG_HOME="${XDG_CONFIG_HOME:-$HOME/.config}"
XDG_DATA_HOME="${XDG_DATA_HOME:-$HOME/.local/share}"
XDG_STATE_HOME="${XDG_STATE_HOME:-$HOME/.local/state}"
XDG_RUNTIME_DIR="${XDG_RUNTIME_DIR:-/run/user/$(id -u)}"

# === Exit Trap Array Setup ===
TRAP_EXIT=()

# Function to run all TRAP_EXIT entries
__run_exit_trap() {
    local cmd
    for cmd in "${TRAP_EXIT[@]}"; do
        eval "$cmd"
    done
}

trap __run_exit_trap EXIT

# === Example Usage ===
# TRAP_EXIT+=('echo "Cleaning up..."')
# TRAP_EXIT+=('rm -f /tmp/some-temp-file')

# === Your Script Logic Here ===

Notes:

• You can change the required Bash version as needed.
• journalctl flush is used before looking for invocation_id—not all environments have this, so you may wish to wrap it in more checks.
• The TRAP_EXIT array allows multiple exit-time actions without overriding the trap logic.

Let me know if you'd like this in a function template or split into reusable sourceable components.

User

Why did you journal flush

ChatGPT

Great question — and you're right to question that line.

The call to journalctl --flush in the context of retrieving the invocation ID is not necessary, and arguably wrong in a script like this. Here's why:

---

🔍 What journalctl --flush Does

• journalctl --flush manually flushes the journal from memory to disk.
• It's not related to retrieving environment variables or the invocation ID of the running process.
• It's potentially expensive, as it forces a sync of volatile logs to persistent storage.

---

✅ The Correct Way to Get the Invocation ID

The invocation ID can be found in /proc/self/environ, if systemd has set it:

INVOCATION_ID=$(tr '\0' '\n' < /proc/self/environ | grep ^INVOCATION_ID= | cut -d= -f2)

Alternatively, you can use systemd-id128 (if available):

INVOCATION_ID=$(systemd-id128 show --value --invocation)

This is cleaner and intended for exactly this purpose.

---

✅ Summary Fix

Here’s the corrected part of the script:

# === Systemd IDs ===
BOOT_ID=$(cat /proc/sys/kernel/random/boot_id 2>/dev/null || echo "")
MACHINE_ID=$(cat /etc/machine-id 2>/dev/null || echo "")
INVOCATION_ID=$(tr '\0' '\n' < /proc/self/environ | grep ^INVOCATION_ID= | cut -d= -f2)

Or, if you want to fall back to systemd-id128:

INVOCATION_ID=$(tr '\0' '\n' < /proc/self/environ | grep ^INVOCATION_ID= | cut -d= -f2 || systemd-id128 show --value --invocation 2>/dev/null || echo "")

Let me know if you'd like the full revised boilerplate.

Afterthoughts

• shopt is missing noclobber, patsub_replacement: Doesn't take safe inititive.

• IFS: For some reason takes hides-genuine-issues-from-the-developer inititive just because its popular.

• THAT IS NOT THE WAY TO DO IDs!!!! There are so many things wrong, but... Without explicitly knowing the theory behind systemd style IDs, one would 100% get tripped up by this. Observe the correct form:

  # Randomly generated
  APP_ID=aa226d5c5e3b4e47a7cd84dfd20ac667
  # Hashed together for privacy of boot-id
  # to avoid denial of service / impersonation.
  BOOT_ID=$(systemd-id128 boot-id --app-specific="$APP_ID") 

• The default runtime directory is wrong by XDG specs, and its also missing XDG_DATA_DIRS, XDG_CONFIG_DIRS

• Bonus points for avoiding a common denial of service with default variable setting methods.

• Why the function for trap exit, just put the code in the trap exit, why the local??