bash: don't add same directory to PATH more than once

path_functions.sh

# bash shell script
# don't add same directory to PATH more than once
#
# EXAMPLES:
#   _bin=${HOME}/bin
#   if [ -d "${_bin}" ]
#       then prepend_path ${_bin}
#   fi
#   
#   append_path ${EPICS_BASE_BIN}
#   append_path ${EPICS_BASE_LIB}


_search_in_path_ () {
    if [ "$#" != "1" ]; then
        echo "usage: _search_in_path_  path"
        exit 1
    fi

    path=$1
    OIFS=$IFS
    IFS=":"
    
    found=""
    read -ra ITEMS <<< "$PATH"
    IFS=$OIFS
    for p in "${ITEMS[@]}"; do
        if [ "$p" == "$path" ]; then
            found+=1
        fi
    done
}

append_path  () {
    if [ "$#" != "1" ]; then
        echo "usage: append_path  path"
        exit 1
    fi

    _search_in_path_ $1
    if [ "$found" == "" ]; then
        export PATH=${PATH}:${path}
    fi
}

prepend_path  () {
    if [ "$#" != "1" ]; then
        echo "usage: prepend_path  path"
        exit 1
    fi

    _search_in_path_ $1
    if [ "$found" == "" ]; then
        export PATH=${path}:${PATH}
    fi
}