aglab.dotfiles/bin/runbg

#!/bin/bash
#systemd-run --user --scope --slice=YukiLauncher.slice --unit="$1-$$".scope /bin/sh -c '"$@"' _ "$@"

# goddamn nvm-sh !!!
# have to update PATH before launch
PATH=$(zsh -c -i 'echo $PATH')
export PATH

# start-bg.sh - robustly start a command in the background and redirect stdout+stderr to a log
# Generated by GitHub Copilot.

# Features:
#  - Uses setsid (preferred) to detach from the controlling terminal.
#  - Falls back to nohup if setsid is unavailable.
#  - Runs the command with stdin closed, stdout+stderr redirected to a logfile.
#  - Sets a safe umask and changes to / to avoid blocking filesystems.
#  - Writes a pidfile next to the log for easy management.
#  - Uses positional args ($@), script PID ($$) and reports child PID ($!).
#
# Usage:
#   start-bg.sh [ -l LOGFILE | -d LOGDIR ] [ -m METHOD ] -- command [args...]
#
# Options:
#   -l, --log LOGFILE      Path to log file (if omitted an auto name is used)
#   -d, --dir LOGDIR       Directory for autogenerated logs (default: ./logs)
#   -m, --method METHOD    Background method: setsid (default) | nohup
#   -h, --help             Show this help and exit
#
# Examples:
#   ./start-bg.sh -- sleep 60
#   ./start-bg.sh -d /var/log/myapp -- /usr/bin/myapp --config /etc/myapp.conf
#   ./start-bg.sh -l ./my.log -- /usr/bin/myapp arg1 arg2

set -euo pipefail

progname=$(basename "$0")

usage() {
  cat <<EOF
Usage: $progname [ -l LOGFILE | -d LOGDIR ] [ -m METHOD ] -- command [args...]

Start "command [args...]" detached from the terminal and redirect stdout+stderr to a log.

METHOD:
  setsid  - use setsid to start a session and detach (preferred)
  nohup   - use nohup (fallback/compat)

When no -l is provided, a log file is auto-generated:
  <LOGDIR>/<command>.<YYYYMMDD-HHMMSS>.pid<$$>.log

A pidfile is written as <logfile>.pid containing the child PID.
EOF
  exit 1
}

# Defaults
logdir="/tmp/$USER/runner"
logfile=""
method="setsid"

# Parse options until the `--` separator
while [[ $# -gt 0 ]]; do
  case "$1" in
    -l|--log)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      logfile="$2"; shift 2 ;;
    -d|--dir)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      logdir="$2"; shift 2 ;;
    -m|--method)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      method="$2"; shift 2 ;;
    -h|--help)
      usage ;;
    --)
      shift; break ;;
    -*)
      echo "Unknown option: $1"; usage ;;
    *)
      break ;;
  esac
done

# Remaining args are the command to run
if [[ $# -eq 0 ]]; then
  echo "Error: no command specified."
  usage
fi

# Preserve the command and args
cmd=( "$@" )
cmd_basename=$(basename "${cmd[0]}")
timestamp=$(date +%Y%m%d-%H%M%S)

mkdir -p -- "${logdir}"

if [[ -z "${logfile}" ]]; then
  logfile="${logdir}/${cmd_basename}.${timestamp}.pid$$.log"
fi

pidfile="${logfile}.pid"

# Validate method
case "${method}" in
  setsid|nohup) ;; 
  *)
    echo "Invalid method: ${method}. Allowed: setsid|nohup"
    exit 2
    ;;
esac

# Prepare environment for child
# We construct a small wrapper for safe daemonization:
start_with_setsid() {
  # Prefer existing setsid binary (coreutils/util-linux)
  if ! command -v setsid >/dev/null 2>&1; then
    return 1
  fi

  # Use setsid to start the process in a new session. We:
  #  - set a conservative umask
  #  - change to / to avoid keeping directories busy
  #  - close stdin and redirect stdout/stderr to logfile
  #
  # We run setsid directly with the command array so arguments are preserved.
  #
  # Note: redirecting >"$logfile" 2>&1 < /dev/null outside ensures the setsid child
  # inherits the redirections.
  (
    umask 022
    cd / || true
    # exec will replace the subshell with the command
    exec "${cmd[@]}"
  ) >"${logfile}" 2>&1 < /dev/null &
  child_pid=$!

  # Detach the job from this shell's job table if possible
  disown "$child_pid" 2>/dev/null || true

  # setsid the already-forked child to start a new session. Some systems allow:
  #   setsid -w <pid>
  # but that's nonportable; instead we try to re-exec the command under setsid.
  # If `setsid` can't be applied to the backgrounded PID, we respawn via setsid:
  if setsid true >/dev/null 2>&1; then
    # Respawn under setsid to ensure proper session leader if available.
    # Kill the previous child (it is still running) and restart under setsid.
    # To avoid races: only do this if cmd is still running and the pid we started is a shell wrapper.
    if kill -0 "$child_pid" 2>/dev/null; then
      # Attempt to terminate wrapper and spawn a true setsid child.
      kill "$child_pid" 2>/dev/null || true
      # Short sleep to allow process cleanup (best-effort)
      sleep 0.05
    fi

    # Now start the real setsid-backed child with same redirections
    setsid "${cmd[@]}" >"${logfile}" 2>&1 < /dev/null &
    child_pid=$!
    disown "$child_pid" 2>/dev/null || true
  fi

  printf '%s' "$child_pid"
  return 0
}

start_with_nohup() {
  # Use nohup as fallback; nohup will ignore HUP but doesn't start a new session.
  nohup "${cmd[@]}" >"${logfile}" 2>&1 < /dev/null &
  child_pid=$!
  disown "$child_pid" 2>/dev/null || true
  printf '%s' "$child_pid"
  return 0
}

# Main launcher: pick method and start
echo "Launching command: ${cmd[*]}"
echo "Log file: ${logfile}"
echo "Method: ${method}"

child_pid=""

if [[ "${method}" == "setsid" ]]; then
  # Try to start via setsid; if setsid not present, fallback to nohup
  if child_pid=$(start_with_setsid); then
    : # success
  else
    echo "setsid not available, falling back to nohup"
    child_pid=$(start_with_nohup)
  fi
else
  child_pid=$(start_with_nohup)
fi

# Write pidfile (best-effort)
if [[ -n "${child_pid}" ]]; then
  printf '%s\n' "${child_pid}" > "${pidfile}" 2>/dev/null || true
fi

# Reporting
echo "Script PID: $$"
if [[ -n "${child_pid}" ]]; then
  echo "Child PID: ${child_pid}"
else
  echo "Child PID: (unknown)"
fi
echo "Pidfile: ${pidfile}"
echo "Started at: $(date --iso-8601=seconds 2>/dev/null || date +%Y-%m-%dT%H:%M:%S%z)"
echo
echo "To follow the log: tail -F ${logfile}"

exit 0