ls-looped

#!/bin/sh

help() { cat <</help
Loop examining file until it stops changing (better than \`watch ls -l FILE')
Usage:  $0 [-TIME] FILE[...]
  TIME is the wait time (default: 10s) between checks (see \`sleep --help')
Example:  ls_looped -5m foobar
ls_looped v 0.4, (c) 2005-9 Adam Katz <scriptsATkhopiscom>, license: GPL v2+
/help
}
# This would probably take 20-50% less code if written with bash arrays,
# but I wanted full POSIX-shell compatibility.  -Adam

def_time=10 # default time in seconds

if [ $# = 0 ] || [ "$1" != "${1#-[-hHVv]}" -a ! -e "$1" ]; then
  help
  exit 0
fi

[ "$1" != "${1#-}" ] && [ -n "$2" ] && time="${1##[-a-z]}" && shift

i=0
while [ $i -lt $# ]; do
  i=$((i+1))
  pending="${pending:-:}$i:"
  unset old old1$i old2$i
done
while [ -n "$1" -a -n "${pending#:}" ]; do

  get_listing() { ls -lpd ${LS_COLORS:+-h} ${LS_COLORS:+--color=always} "$@";}
  if [ $# = 1 ]
    then
      listing=`get_listing "$@"`
      printf "\r$(echo $listing)"
    else
      clear 2>/dev/null
      if [ "${time:-1}" -gt 0 ] 2>/dev/null
        then tmp="${time:-$def_time}s"
        else tmp="$time"
      fi
      tmp="$tmp looped listing of: $*"
      tmp2=`date +"%a %b %e %T %Y"`
      width="$((${#tmp}+${#tmp2}+4-${COLUMNS:-80}))" 2>/dev/null
      if ! [ "$width" -le 0 ] 2>/dev/null; then # we use ! ge to catch errors
        tmp3=`echo "$tmp" |sed -r "s/.{$width}$//" 2>/dev/null`
        if [ -z "$tmp3" ]; then
          tmp3="$tmp"
          i="$width"
          while [ "$i" -gt 0 ]; do
            tmp3="${tmp3%?}"
            i="$((i-1))"
          done
        fi
        tmp="$tmp3..."
      fi
      echo "$tmp $tmp2"
      get_listing "$@"
  fi

  # sleep for specified time; if it failed, reset time to 10s and use that
  if ! sleep $time 2>/dev/null; then time="$def_time"; sleep $time; fi

  i=1
  for file in "$@"; do

    listing=`ls -ln --full-time "$file" 2>/dev/null || ls -l "$file"`
    #eval old='$'old2$i    # dash breaks POSIX std: http://tinyurl.com/n5r62o
    old="old2$i"
    old=`eval echo '$'$old`

    tmp1="${pending%:$i:*}"     # i=3 pending=:1:2:3:4: -> tmp1=:1:2
    if [ "$listing" = "$old" ]  # unchanged after three of the same
    then
      tmp2="${pending#*:$i:}"   # i=3 pending=:1:2:3:4: -> tmp2=4:
      if [ -z "$tmp1$tmp2" ]    # we have no pending files
        then unset pending      # done
      elif [ "$tmp1" != "$tmp2" ]   # if tmp1 and tmp2 are different
        then pending="$tmp1:$tmp2"      # concatenate;  ... -> pending=:1:2:4:
      fi  # (otherwise, there was no hit and we should do nothing)
    else                # changed
      if [ "$pending" = "$tmp1" ]; then # if changed but marked as unchanging
        pending="${pending:-:}$i:"    # add i back to pending list
      fi
    fi

    #eval old2$i='$'old$i   # dash breaks POSIX standard as noted above
    old="old1$i"
    old=`eval echo '$'$old`
    export old2$i="$old"
    export old1$i="$listing"

    i=$((i+1))
  done

done

if [ $# = 1 ]; then
  echo "" # the \n to end the last line
fi