Prune duplicate entries from PATH variable

Use the pathmunge() function available in most distro's /etc/profile:

pathmunge () {
if ! echo $PATH | /bin/egrep -q "(^|:)$1($|:)" ; then
   if [ "$2" = "after" ] ; then
      PATH=$PATH:$1
   else
      PATH=$1:$PATH
   fi
fi
}

edit: For zsh users, typeset -U <variable_name> will deduplicate path entries.

I was having this issue so I used a combination of techniques listed on StackOverflow question. The following is what I used to dedupe the actual PATH variable that had already been set, since I didn't want to modify the base script.

    tmppath=(${PATH// /@})
    array=(${tmppath//:/ })
    for i in "${array[@]//@/ }"
    do
        if ! [[ $PATH_NEW =~ "$i" ]]; then
            PATH_NEW="${PATH_NEW}$i:";
        fi
    done;
    PATH="${PATH_NEW%:}"
    export PATH
    unset PATH_NEW

You could always optimize this a bit more, but I had extra code in my original to display what was happening to ensure that it was correctly setting the variables. The other thing to note is that I perform the following

1. replace any SPACE character with an @ character
2. split the array
3. loop through the array
4. replace any @ characters in the element string with a space

This is to ensure that I can handle directories with spaces in (Samba home directories with Active Directory usernames can have spaces!)

Set your path explicitly.