#!/bin/bash
###########################################################
## Remove duplicate tokens in a PATH-like variable and spit it back out.
## Usage: pathtok [-v] [-r] [-p VARNAME]|[LIST]
##   -r           allow relative paths (including ".")
##   -p VARNAME   parse VARNAME (e.g. "PATH") instead of a LIST
##   -V           print version info and exit
##   LIST         a list tokenized with colons, like "/home/bin:/usr/bin:/bin"
## Filter your path with commands like: export PATH=`pathtok $PATH`
## pathtok 3.0, Copyright (c) 2006 by Adam Katz <scripts@khopis.com>, GPL
#########
#### Changelog:
#### 1.0)  It works, reliably, but horribly inefficient
#### 2.0)  Complete re-write.  still inefficient, but faster
#### 3.0)  Complete re-write, no grep/sed/awk in loop, no files.  now EFFICIENT!
####       Caveat:  requires bash for variable substitution ${var/find/replace}
###########################################################

IAM=`which $0 2>/dev/null || echo $0`
IAM2=`basename $IAM`

help() {
  grep "^## " "$IAM" |sed 's/^#*.//'
}

# loop through arguments, parsing options until we hit first non-option
while [ -n "$1" ]; do
 case $1 in
  [^-]* ) break ;;	# first non-option param is LIST (up top for speed)
  -h* | --h* ) help; exit 0 ;;
  -var | --var* | -p* | --p* ) 
    if [ -n "$2" ]
      then VAR=$2; shift
      else echo "$IAM2: Option \`$1' needs VARNAME, like \`$1 PATH'" >&2; exit 1
    fi ;;
  -r* | --r* ) export relative=true ;;		# ignore absoluteness test
  -V | --ver ) help |tail -n1; exit 0 ;;	# version is last line of help
  -* ) echo "$IAM2: Invlaid argument \`$1'" >&2; 
       help |grep Usage |cat; exit 1 ;;	# (cat removes grep's color if any)
  * ) break ;;		# default case, just in case top one failed
 esac
 shift
done


if [ -n "$VAR" ] 
  # set 'arguments' to content of variable named by $VAR (ie, dereference VAR)
  #then set no-options $(eval echo $`echo $VAR`); shift
  then set no-options ${!VAR}; shift  # bash does this built-in!! (zsh does NOT)
fi

# if without arguments, default LIST to current $PATH
[ -z "$*" ] && set $PATH

p=:
# loop through paths in LIST
for dir in ${*//:/ }; do # bash substitution was: $(echo $* |sed 's/:/ /g')
  # if dir is a directory, not yet in p, and (absolute, unless relative is okay)
  # (compare variables to substitutions that do nothing in these cases)
  if [ -d "$dir" ] && [ "$p" = "${p/:$dir:/}" ] \
    && ( [ -n "$relative" ] || [ "$dir" = "/${dir#?}" ] )
    then p="$p$dir:"
  fi
done

p=${p#:} # remove extraneous first delimiting colon (can't nest these...)
echo ${p%:} # remove extraneous last delimiting colon and echo result