fs/skeleton/usr/bin/find

#!/bin/sh
# A really simple implementation of find, for those of us without busybox
# or the desire to include the oversized GNU one.
#
# WARNING: the symlink-avoidance feature may have race conditions.  Try
# not to use this tool for anything important.
#

usage()
{
  echo "Usage: $0 <paths>" >&2
  echo "  Unlike a real version of 'find', this program has no options." >&2
}


startswith()
{
  [ "${1#"$2"}" != "$1" ]
  return $?
}


do_find_onedir()
{
  local prefix="$1"

  # Yes, due to oddities of sh parsing rules, this loop is actually safe
  # for filenames containing spaces.  (It will also work with filenames
  # containing newlines, but find separates output lines with newline, so
  # that's still not useful.)
  for d in * .*; do
    [ "$d" = "." ] && continue
    [ "$d" = ".." ] && continue
    if [ -L "$d" ] || [ -e "$d" ]; then  # skip '*' and '.*' in empty dir
      echo "$prefix/$d"
    fi
    if [ -d "$d" ] && [ ! -L "$d" ]; then
      cd "$d" && {
        do_find_onedir "$prefix/$d"
        cd ..
      }
    fi
  done
}


do_find()
{
  for d in "$@"; do
    # Normally I would use () instead of {} here, to remove the need for
    # the possibly-bug-inducing 'cd ..' step.  However, () requires a fork,
    # which causes a fairly significant slowdown in this already-slow
    # implementation of find.
    cd "$d" && {
      echo "$d"  # find should always print the directory itself first
      do_find_onedir "${d%/}"
      cd ..
    }
  done
}


# Check command line validity
for d in "$@"; do
  startswith "$d" "-" && usage
done


if [ $# = 0 ]; then
  do_find .
else
  do_find "$@"
fi