watch-and-run

#!/bin/bash

die() { echo "$*"; exit 1; }

main() {
  program=$0

  [[ $# -ge 2 ]] ||
    die "usage: $program <watch-file> <command> [<command-args>]"
  file=${1:?first arg must be file path}; shift
  type "$1" &>/dev/null ||
    die "second arg must be valid command"

  export WATCH_AND_RUN_FILE=$file

  mark=$(mktemp)

  run-loop "$@" &

  echo "PID = $!"
}

run-loop() {
  while true; do
    if [[ $file -nt $mark ]]; then
      touch "$mark"

      echo
      echo "Changed: $file"
      echo "Running: $*"

      "$@"
    fi

    sleep 0.1
  done
}

[[ $0 != "$BASH_SOURCE" ]] || main "$@"

# vim: set ft=sh: