pathmangle.sh

#! /bin/bash

IFS_BAK=$IFS
IFS=':'

is_include () {
    l=$1
    e=$2
    for p in $l; do
        if [ "$p" == "$e" ]; then
            return 0
        fi
    done
    return 1
}

append_head () {
    l=$1
    h=$2
    if [ -z "$l" ]; then
        echo "$h"
    elif is_include "$l" "$h"; then
        echo "$l"
    else
        echo "$h:$l"
    fi
}

append_tail () {
    l=$1
    t=$2
    if [ -z "$l" ]; then
        echo "$t"
    elif is_include "$l" "$t"; then
        echo "$l"
    else
        echo "$l:$t"
    fi
}

newpath=""

for p in $PATH; do
    if [ -d "$p" ]; then
        if echo "$p" | grep cabal > /dev/null; then
            newpath=$(append_head "$newpath" "$p")
        else
            newpath=$(append_tail "$newpath" "$p")
        fi
    fi
done

echo "$newpath"

IFS=$IFS_BAK