#!/bin/sh
#
# Background a command.
# Copy output to a log.
# Record the pid in a file.
# NoHUP it.
#	- Cameron Simpson <cs@zip.com.au> 25aug1999
# 

: ${LOGDIR:=$HOME/var/log}
: ${CONSOLE:=$LOGDIR/console}
: ${VARRUN:=$HOME/var/run}

cmd=`basename "$0"`

input=/dev/null
logfile=$CONSOLE
pidfile=
ignhup=1
async=1

usage="Usage: $cmd [-i input] [-l logfile] [-p pidfile] [-s] command [args...]
	-i input	Input path.
			\"-\" means don't change stdin.
			Default: $input
	-l logfile	Output and error output path.
			\"-\" means don't change stdout or stderr.
			Default, from \$CONSOLE: $logfile
	-p pidfile	File to hold process id.
			\"-\" means write the pid to stdout.
			\"\" means write the pid file to \$VARRUN/command@\$HOST
	-s		Synchronous - wait for the process to terminate.
			Default: asynchronous."

badopts=
while :
do  case $1 in
      -i)	input=$2; shift ;;
      -l)	logfile=$2; shift ;;
      -p)	pidfile=$2; shift ;;
      -s)	async= ;;
      --)	shift; break ;;
      -?*)	echo "$cmd: unrecognised option: $1" >&2
		badopts=1
		;;
      *)	break ;;
    esac
    shift
done

if [ $# = 0 ]
then
    echo "$cmd: missing command" >&2
    badopts=1
fi

[ $badopts ] && { echo "$usage" >&2; exit 2; }

command=$1
combase=`basename "$command"`

[ -n "$logfile" ] || logfile=$combase@$HOST
[ -n "$pidfile" ] || pidfile=$combase@$HOST

case $logfile in -|/*) ;; *) logfile=$LOGDIR/$logfile ;; esac
case $pidfile in -|/*) ;; *) pidfile=$VARRUN/$pidfile ;; esac

## echo "logfile=$logfile, pidfile=$pidfile"

exec 9<&0
(
  if [ "x$input" = x- ]
  then  exec <&9
  else  exec <"$input"
  fi
  exec 9<&-

  [ "x$logfile" = x- ] || exec >>"$logfile" 2>&1

  [ $ignhup ] && trap '' 1
  [ $async ] && trap '' 2

  exec "$@"
) &
pid=$!

# close input just in case
exec <&-

( [ "x$pidfile" = x- ] || exec >"$pidfile"
  echo "$pid"
)

[ $async ] || wait