ds-common

#!/bin/sh
log() { echo ${prog} $(date +%F_%T) "$@" >> /home/user/xxx; }
fail() { err=$1; log Error "${@}"; exit $err; }
all2log() { exec >> /home/user/xxx 2>&1; }
prog=$(basename $0)
progdir=$(cd `dirname $0`;pwd); d=$progdir
pid=$$
[ "$prog" = "ds-common" ] && { echo Do not run ds-common directly; exit 99; }
[ $(id -u) -eq 0 ] || exec sudo ${progdir}/$prog "$@"
log Started $@

while [ $@ ]; do
  if ([ "$1" = "LOOP" ]); then
    loop_mode=true; log Will go into loop_mode
  fi
  type -t args_core && args_core
  shift
done

loop_delay=60
loop() {
  [ $loop_mode ] || { nohup "$0" LOOP& exit 0; }
  get_lock $2
  log going loopy pid=${pid}
  while :; do
    test_lock $LOCKFILE
    loop_core
    gap=$loop_delay
    sleep $gap
  done
}

get_lock() {
  [ "x$LOCKFILE" = "x" ] && LOCKFILE=${1:-/tmp/$prog.lock}
  [ -f "$LOCKFILE" ] && { log Lockfile already exists - exiting; exit 0; }
  echo $progdir/$prog $$ > $LOCKFILE; sleep 1
  grep -q " ${pid}$" $LOCKFILE || { log Someone else got the lock before me; exit 0; }
}

test_lock() {
  grep -q " ${pid}$" $LOCKFILE 2>/dev/null || { log My log has vanished or been stollen; exit 0; }
}