file_repl.sh

#!/bin/bash
# -*- coding: utf-8, tab-width: 2 -*-


function file_repl () {
  export LANG{,UAGE}=en_US.UTF-8  # make error messages search engine-friendly
  local SELFPATH="$(readlink -m -- "$BASH_SOURCE"/..)"
  cd -- "$SELFPATH" || return $?
  local BFN="$FUNCNAME.$(printf '%(%y%m%d-%H%M%S)T' -1)-$$"
  local DEFAULT_SCAN_INTV=10
  local DELAY=2 # How long to give job files to settle on disk.
  exec </dev/null
  >>"$BFN".pid
  sleep "$DELAY" || true
  local REN='mv --no-clobber --no-target-directory --'
  local INTV= JOB= FEXT=
  while [ -f "$BFN".pid ]; do
    echo "D: $FUNCNAME[$$] scan $BFN.*"
    for JOB in "$BFN".*.{rc,sh}; do
      [ -f "$JOB" ] || continue
      echo "D: $FUNCNAME[$$] $JOB"
      FEXT="${JOB##*.}"
      JOB="${JOB%.*}"
      sleep "$DELAY" || true
      $REN "$JOB".{$FEXT,wip} || continue
      case "$FEXT" in
        rc ) source -- "$JOB".wip &>"$JOB".log; job_done $?;;
        sh ) one_job & disown $!;;
      esac
    done
    [ "$INTV" != quit ] || break
    [ "${INTV:-0}" -ge 1 ] || INTV="$DEFAULT_SCAN_INTV"
    echo "D: $FUNCNAME[$$] wait $INTV"
    sleep "$INTV"s || return $?
  done
  rm -- "$BFN.pid" 2>/dev/null
  echo "D: $FUNCNAME[$$] quit"
}


function one_job () {
  echo "D: $FUNCNAME[$$] $*"
  echo "<< $FUNCNAME[$$] >>" >>"$JOB".log
  timeout --signal=TERM --kill-after=1m 1h bash "$JOB".wip &>>"$JOB".log
  job_done $?
}


function job_done () {
  local RV=$1
  printf '\n%(%T %F)T rv=%s\n' -1 "$RV" >>"$JOB".log
  local FEXT='done'
  [ "$RV" == 0 ] || FEXT="err-$RV"
  $REN "$JOB".{wip,"$FEXT"}
}









# Fork off so we can run this from an NTFS network share without having
# the parent shell holding a lock on the file.
file_repl "$@" & disown $!; exit 0