#!/bin/bash
#
# find_working: Find a version of some tool in the PATH which actually runs.
# Usage: find_working [options] <prog>
# Options: -A          Don't test arguments to executable files.
#          -a <args>   Use arguments to test executable files.  Default --help.
#          -g <re>     Search string in <args> output.  Default <prog>.
#          -q          Don't print path to prog.  Just exit 0 if found.
#          -x          Don't try to execute unreadable files.  Assume success.
#          -X          Don't try to execute unreadable files.  Assume failure.
#

args="-h -? --help"
quiet=0
unreadable=
re=
while getopts ":Aa:g:qxX" opt; do
  case $opt in
    A) args="";;
    a) args="$OPTARG";;
    g) re="$OPTARG";;
    q) quiet=1;;
    x) unreadable=0;;
    X) unreadable=1;;
  esac
done
shift $((OPTIND-1))

prog="$1"; shift
if [ -z "$prog" ]; then
  echo >&2 "Usage: find_working [options] <prog>"
  echo >&2 "Options: -A          Don't test arguments to executable files."
  echo >&2 "         -a <args>   Use arguments to test executable files.  Default --help."
  echo >&2 "         -g <re>     Search string in <args> output.  Default <prog>."
  echo >&2 "         -q          Don't print path to prog.  Just exit 0 if found."
  echo >&2 "         -x          Don't try to execute unreadable files.  Assume success."
  echo >&2 "         -X          Don't try to execute unreadable files.  Assume failure."
  exit 1
fi

[ -z "$re" ] && re="\\b$prog\\b"

# Default args contain -? which might be interpreted as a glob.
set -o noglob

ret=
for path in ${PATH//:/ }; do
  [ -x "$path/$prog" ] || continue

  if [ -r "$path/$prog" ]; then
    if [ -n "$args" ]; then
      "$path/$prog" $args 2>&1 | grep "$re" >/dev/null || continue
    else
      ldd "$path/$prog" 2>/dev/null | grep "not found" >/dev/null && continue
    fi
    ret="$path/$prog"
    break
  elif [ -z "$unreadable" ]; then
    "$path/$prog" $args 2>&1 | grep "$re" >/dev/null || continue
    ret="$path/$prog"
    break
  elif [ $unreadable = 0 ]; then
    ret="$path/$prog"
    break
  elif [ $unreadable = 1 ]; then
    continue
  fi

  exit 0
done

if [ -n "$ret" ]; then
  [ $quiet = 0 ] && echo "$ret"
  exit 0
fi

exit 100